There are short term tracking apps like Glympse for locating people around you( who use glympse). There are hundreds of simple trackers on the playstore, the hard part is getting people to use them and trust them ( which they shouldn't) . background services can send location data from other apps that use the location sensor.
Me and a bunch of other chaps used EchoEcho to keep tabs on each other a few years back on a motorbike tour around the north island. We found it very effective except when I enabled false location reporting for a bit of a giggle - took them a while to work out that I wasn't miles ahead of them with my feet up :-)
All parties must have the app installed. Essentially you ping someone with a location request and they can choose to answer or not. If they do, their location is reported to you. Conversely you can send your location to others who have the app installed.
Edit: everyone uninstalled the app after the tour as it was no longer needed.