Hands-free interface

1. A method comprising:

a wearable device receiving from an external reader a level of radiant energy;

the wearable device detecting a change in the received level of radiant energy;

the wearable device determining that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy, wherein determining that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy comprises determining that the detected change in the received level of radiant energy is indicative of at least one body movement; and

in response to the determining, the wearable device transmitting to the external reader an instruction that indicates that the wearable device has determined that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy.

2. The method of claim 1 ,

wherein receiving a level of radiant energy comprises receiving a level of light incident on a light detector associated with the wearable device.

3. The method of claim 1 ,

wherein receiving a level of radiant energy comprises receiving a level of radio frequency (RF) radiation from the external reader.

4. The method of claim 1 , wherein determining that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy comprises determining that some combination of two or more of the following has occurred:

the received level of radiant energy has, within a threshold period of time, changed from a first level to a second level and then returned to at or near the first level,

the received level of radiant energy has changed from a first level to a second level and then remained at the second level for at least a threshold period of time, and

the received level of radiant energy has, over a period of time greater than or equal to a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.

5. The method of claim 1 , wherein the wearable device transmitting to an external reader an instruction causes the external reader to transmit an instruction to at least one external device.

6. The method of claim 1 , wherein the at least one body movement comprises a blink, a nod, or a change of gaze.

7. The method of claim 6 , wherein the at least one body movement comprises a blink, wherein determining that the detected change in the received level of radiant energy is indicative of a blink comprises:

determining that the received level of radiant energy has, within a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.

8. The method of claim 6 , wherein the at least one body movement comprises a change of gaze, wherein determining that the detected change in the received level of radiant energy is indicative of a change of gaze comprises:

determining that the received level of radiant energy has changed from a first level to a second level and then remained at the second level for at least a threshold period of time.

9. The method of claim 6 , wherein the at least one body movement comprises a nod, wherein determining that the detected change in the received level of radiant energy is indicative of a nod comprises:

determining that the received level of radiant energy has, over a period of time greater than or equal to a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.

10. A method comprising:

a reader device transmitting to a wearable device radiant energy;

in response to the transmitting, the reader device receiving from the wearable device one or more signals indicative of a change in a received level of the radiant energy from the reader device;

the reader device determining that the change in the received level of the radiant energy from the reader device is indicative of a predetermined pattern of received radiant energy, wherein determining that the change in the received level of the radiant energy from the reader device is indicative of a predetermined pattern of received radiant energy comprises determining that the change in the received level of the radiant energy from the reader device is indicative of at least one body movement; and

in response to the determining, the reader device operating at least one external device.

11. The method of claim 10 ,

wherein the reader device receiving from the wearable device one or more signals indicative of a change in a received level of the radiant energy from the reader device comprises:

the reader device receiving from the wearable device one or more signals indicative of levels of the radiant energy from the reader device received at the wearable device; and

based on the one or more signals, the reader device detecting a change in the received level of the radiant energy from the reader device at the wearable device.

12. The method of claim 11 ,

wherein the levels of the radiant energy from the reader device received at the wearable device comprise levels of light incident on a light detector associated with the wearable device.

13. The method of claim 11 ,

wherein the levels of the radiant energy from the reader device received at the wearable device comprise levels of radio frequency (RF) radiation received from the reader device.

14. The method of claim 10 ,

wherein the reader device receiving from the wearable device one or more signals indicative of a change in a received level of the radiant energy from the reader device comprises:

the reader device receiving from the wearable device a level of backscatter radiation; and

the reader device detecting a change in the received level of backscatter radiation.

15. The method of claim 10 , wherein determining that the change in the received level of the radiant energy from the reader device is indicative of a predetermined pattern of received radiant energy comprises determining that some combination of two or more of the following has occurred:

the received level of the radiant energy from the reader device has, within a threshold period of time, changed from a first level to a second level and then returned to at or near the first level,

the received level of the radiant energy from the reader device has changed from a first level to a second level and then remained at the second level for at least a threshold period of time, and

the received level of the radiant energy from the reader device has, over a period of time greater than or equal to a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.

16. The method of claim 10 , wherein the at least one body movement comprises a blink, a nod, or a change of gaze.

17. The method of claim 16 , wherein the at least one body movement comprises a blink, wherein determining that the change in the received level of the radiant energy from the reader device is indicative of a blink comprises:

determining that the received level of the radiant energy from the reader device has, within a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.

18. The method of claim 16 , wherein the at least one body movement comprises a change of gaze, wherein determining that the change in the received level of the radiant energy from the reader device is indicative of a change of gaze comprises:

determining that the received level of the radiant energy from the reader device has changed from a first level to a second level and then remained at the second level for at least a threshold period of time.

19. The method of claim 16 , wherein the at least one body movement comprises a nod, wherein determining that the change in the received level of the radiant energy from the reader device is indicative of a nod comprises:

determining that the received level of the radiant energy from the reader device has, over a period of time greater than or equal to a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.

20. A system comprising:

a wearable device comprising an antenna; and

a reader device,

wherein the wearable device is configured to:

receive a level of radiant energy from the reader device;

detect a change in the received level of radiant energy;

determine that the detected change is indicative of a predetermined pattern of received radiant energy, wherein determining that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy comprises determining that the detected change in the received level of radiant energy is indicative of at least one body movement; and

in response to the determining, operate the antenna to transmit to the reader device an instruction that indicates that the wearable device has determined that the detected change in the received level of radiant energy is indicative of a predetermined pattern of received radiant energy, and

wherein the reader device is configured to:

receive the instruction from the wearable device; and

in response to the receiving, operate at least one external device.

21. The system of claim 20 , further comprising:

an auxiliary device comprising an inductive sensor, wherein the auxiliary device is configured to:

determine a level a level of inductance of the inductive sensor based on the proximity of the wearable device to the auxiliary device;

detect a change in the level of inductance;

determine that the determined change is indicative of a predetermined pattern of determined inductance; and

transmit to the reader device an auxiliary instruction that indicates that the auxiliary device has determined that the detected change in the level of inductance is indicative of a predetermined pattern of determined inductance, and

wherein the reader device is further configured to:

receive the auxiliary instruction from the auxiliary device; and

in response to the receiving, operate at least one external device.

22. The system of claim 20 , wherein the wearable device is configured to determine that the detected change is indicative of a predetermined pattern of received radiant energy comprises determining that some combination of two or more of the following has occurred:

the received level of radiant energy has, within a threshold period of time, changed from a first level to a second level and then returned to at or near the first level,

the received level of radiant energy has changed from a first level to a second level and then remained at the second level for at least a threshold period of time, and

the received level of radiant energy received has, over a period of time greater than or equal to a threshold period of time, changed from a first level to a second level and then returned to at or near the first level.