The 21st Century's Most Dangerous Game

Some of you might know the story of the Most Dangerous Game by Richard Connell, featuring Sanger Rainsford and General Zaroff. To make a long story short, Rainsford is stranded on Zaroff's island and hunted by him. Rainsford has few supplies and has to rely on his wits to set a trap for Zaroff and kill him. About two years ago, the Achievement Hunter team did something similar in Minecraft and Grand Theft Auto V, and I was thinking that it would be cool to make it an IRL thing with a modern twist on it. The trouble is, both MC and GTA have maps with the character's real-time position on them, and the only way I know of that would give people that IRL is a GPS tracker app for their phones. But, I don't know of any good ones that can be updated real-time and accessed from the phone itself, rather than a computer, and are cross platform. Does anyone have any good suggestions?
The requirements for this app are:
Must be cross-compatible with Android and iOS

UPDATE: I know of Life 360 and Glympse, but I'm looking for more suggestions.
Must be able to access the map data from the app instead of having to use a computer
Must be updateable in real-time