Patent ID: 8688779

Claim:
A user device comprising: an output interface for transmitting data to a plurality of other user devices of a peer-to-peer data sharing group, the data sharing group comprising at least two user devices other than the user device, each user device of the data sharing group configured to store data shared by user devices of the data sharing group on the respective user device and to maintain a list of the user devices in the data sharing group, wherein the data stored by each user device of the data sharing group enables access to location data for other user devices of the data sharing group without contacting a server; 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 plurality of other user devices of the data sharing group; and outside the limited length of time, cease to periodically provide location data for the user device to the output interface, 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 plurality of other user devices of the data sharing group without the location data being retained by a server, the single message containing the location data and addresses of the plurality of other user devices of the data sharing group, wherein the user device subsequently receives from the relay or router a delivery acknowledgment when each of the plurality of other user devices of the data sharing group receives the single message.