Glympse - Glympse is the easy way to safely share your location in realtime. No sign-up needed.
Mapme - Build smart and beautiful maps within minutes with no coding.
Zenly - Zenly is a GPS tracker to locate your friends in realtime.
Touch GIS - The premier tool for mobile field data collection and visualization. Available for iPhone & iPad.
OwnTracks - Cross-platform location sharing
Reactive Maps - Build awesome maps with reusable UI + data components.