Techniques for determining and communicating presence

1. An apparatus, comprising:

a processor circuit;

a hardware communications component; and

a presence component operative on the processor circuit to determine whether a first user is present to receive a first short message service (SMS) message on a mobile device in response to a second user requesting a social networking web page containing profile information for the first user, wherein the first user and the second user have a defined relationship in a social networking service, and to perform periodic attempts to transmit partial SMS messages to the mobile device via the hardware communications component and to update a presence record for the first user based on the attempts to transmit, wherein the partial SMS messages are separate from the first SMS message and comprise a header comprising a command to request a response, and to delay the periodic attempts to transmit the partial SMS messages when the presence component determines that the first user has successfully transmitted or received a second SMS message using the mobile device; and

a display component operative on the processor circuit to indicate to the second user whether the first user is present to receive the first SMS message on the mobile device.

2. The apparatus of claim 1 , the display component operative to include a SMS presence indicator for the first user in the social networking web page transmitted to the second user, the SMS presence indicator indicating whether the first user is present to receive the first SMS message on the mobile device.

3. The apparatus of claim 2 , the SMS presence indicator indicating an amount of time since the first user was determined to be present to receive the first SMS message on the mobile device.

4. The apparatus of claim 1 , the presence component operative to transmit a partial SMS message to the mobile device, to receive a response to the partial SMS message from the mobile device, and to determine that the first user is present to receive the first SMS message on the mobile device based on the received response to the partial SMS message.

5. The apparatus of claim 1 , the presence component operative to initiate transmission of a partial SMS message to the mobile device, to determine that the transmission to the mobile device has failed, and to determine that the first user is not present to receive the first SMS message on the mobile device based on the failed transmission to the mobile device.

6. The apparatus of claim 1 , the display component operative to indicate to the second user whether the first user is present to receive the first SMS message on the mobile device based on the presence record.

7. The apparatus of claim 1 , the presence component operative to determine whether the first user is present to receive the first SMS message on the mobile device in response to the second user initiating composition of a message to the first user.

8. A computer-implemented method, comprising:

transmitting, periodically, a partial short message service (SMS) message to a mobile device of a first user in response to a second user requesting a social networking web page containing profile information for the first user, wherein the first user and the second user have a defined relationship in a social networking service, wherein the partial SMS message comprises a header comprising a command to request a response;

receiving a response to the partial SMS message from the mobile device;

updating a presence record for the first user based on the transmitting;

determining whether the first user is present to receive a first SMS message on the mobile device based on the received response to the partial SMS message;

delaying the periodic transmittals of the partial SMS messages when the first user has successfully transmitted or received a second SMS message using the mobile device; and

indicating to the second user whether the first user is present to receive the first SMS message on the mobile device.

9. The method of claim 8 , comprising:

including a SMS presence indicator for the first user in the social networking web page transmitted to the second user, the SMS presence indicator indicating whether the first user is present to receive the first SMS message on the mobile device and an amount of time since the first user was determined to be present to receive the first SMS message on the mobile device.

10. The method of claim 8 , comprising:

initiating transmission of the partial SMS message to the mobile device;

determining that the transmission to the mobile device has failed; and

determining that the first user is not present to receive the first SMS message on the mobile device based on the failed transmission to the mobile device.

11. The method of claim 8 , comprising:

determining whether the first user is present to receive the first SMS message on the mobile device in response to the second user initiating composition of a message to the first user.

12. At least one non-transitory computer-readable storage medium comprising instructions that, when executed, cause a system to:

transmit, periodically, a partial short message service (SMS) message to a mobile device of a first user in response to a second user requesting a social networking web page containing profile information for the first user, wherein the first user and the second user have a defined relationship in a social networking service, wherein the partial SMS message comprises a header comprising a command to request a response;

receive a response to the partial SMS message from the mobile device;

determine whether the first user is present to receive a first short message service (SMS) message on the mobile device based on received response to the partial SMS message;

update a presence record for the first user based on the transmitting;

delay the periodic transmittals of the partial SMS message when the first user has successfully transmitted or received a second SMS message using the mobile device; and

indicate to the second user whether the first user is present to receive the first SMS message on the mobile device.

13. The non-transitory computer-readable storage medium of claim 12 , comprising instructions that when executed cause the system to:

determine that the transmission of the partial SMS message to the mobile device has failed; and

determine that the first user is not present to receive the first SMS message on the mobile device based on the failed transmission to the mobile device.

14. The non-transitory computer-readable storage medium of claim 12 , comprising instructions that when executed cause the system to:

determine whether the first user is present to receive the first SMS message on the mobile device in response to the second user initiating composition of a message to the first user.