Publishing location for a limited time

1. A user device comprising:

an output interface for transmitting data to at least one other user device;

a user interface configured to receive an instruction to enable periodic location data sharing of location data for the user device for a limited length of time after which location sharing is to be disabled; and

a location sharing module configured to:

during the limited length of time, periodically provide location data for the user device to the output interface to be transmitted to the at least one other user device; and

outside the limited length of time, cease to periodically provide location data for the user device to the output interface;

wherein the instruction to enable periodic location data sharing of location data for the user device for a limited length of time defines a bounded length of time starting from a time at which the instruction is received; and

wherein periodically providing location data for the user device to the output interface comprises:

periodically sending a single message to a relay or router for independent distribution to the at least one other user device without the location data being retained by a server, the single message containing the location data and addresses of the at least one other user device, wherein the user device subsequently receives from the relay or router a delivery acknowledgment when each of the at least one other user device receives the single message.

2. The user device of claim 1 , wherein the user interface permits selection of the bounded length of time from a set of predefined time lengths.

3. The user device of claim 2 , wherein the set of predefined time lengths is presented as a list.

4. The user device of claim 2 , wherein the set of predefined time lengths comprises 30 minutes, 1 hour, 2 hours, and 4 hours.

5. The user device of claim 2 , wherein the user interface permits manual entry of the bounded length of time.

6. The user device of claim 1 , further comprising a touch display screen for presenting the user interface and receiving the instruction.

7. The user device of claim 1 , further comprising a location determination system from which the location sharing module receives the location data.

8. The user device of claim 7 , wherein the location determination system comprises a GPS (Global Positioning System) receiver.

9. A method for limiting a time for which location data sharing is enabled for a user device, the method comprising:

receiving an instruction through a user interface on the user device indicating that periodic location data sharing of location data for the user device is to be enabled for a limited length of time after which location sharing is to be disabled;

during the limited length of time, periodically obtaining location data for the user device and periodically transmitting the location data to at least one other user device; and

outside the limited length of time, cease periodically transmitting the location data;

wherein the instruction to enable periodic location data sharing of location data for the user device for a limited length of time defines a bounded length of time starting from a time at which the instruction is received; and

wherein periodically transmitting the location data to the at least one other user device comprises:

periodically sending a single message to a relay or router for independent distribution to the at least one other user device without the location data being retained by a server, the single message containing the location data and addresses of the at least one other user device, wherein the user device subsequently receives from the relay or router a delivery acknowledgment when each of the at least one other user device receives the single message.

10. A non-transitory computer readable medium having computer executable instructions store thereon, that when executed cause a processor to implement a method for limiting a time for which location data sharing is enabled for a user device, the method comprising:

receiving an instruction through a user interface on the user device indicating that periodic location data sharing of location data for the user device is to be enabled for a limited length of time after which location sharing is to be disabled;

during the limited length of time, periodically obtaining location data for the user device and periodically transmitting the location data to at least one other user device; and

outside the limited length of time, cease periodically transmitting the location data;

wherein the instruction to enable periodic location data sharing of location data for the user device for a limited length of time defines a bounded length of time starting from a time at which the instruction is received; and

wherein periodically transmitting the location data to the at least one other user device comprises:

periodically sending a single message to a relay or router for independent distribution to the at least one other user device without the location data being retained by a server, the single message containing the location data and addresses of the at least one other user device, wherein the user device subsequently receives from the relay or router a delivery acknowledgment when each of the at least one other user device receives the single message.