PlaceTrack is a multi-client location sharing platform supporting a rich feature-set including:

• safe location sharing with trusted people, in real time
• secure, redundant, backend infrastructure
• passive and battery friendly: mobile apps run in the background with no noticeable impact on battery life using all available state-of-the-art technologies of the underlying mobile platform (geofencing, significant location change, etc)
• push/pull mode: a contact’s device can be forced to immediately send a fresh location (otherwise locations is updated as they move)
• rich data: real time sharing can include current location, location history, speed, altitude, current o/s and device battery level, whether you’re walking, running, moving in a vehicle or resting
• delayed sync: stores your locations when network is unreachable and pushes them to the PlaceTrack servers when you’re back online
• user authentication using phone number verification through SMS code
• developer API planned to be released to the public in early 2015

http://placetrack.me