“Cheating” is not an easy thing to do; every time your employees send an event, their position (acquired by GPS, WiFi and GSM cell antennas) and respective time-stamp is also included, so you will be able to spot where they are.

There are more ways to ensure you get accurate results: you can use different kinds of checkpoints (like Beacons which can be placed in unreachable areas) or make use of the Geofence feature which instantly highlights a checkpoint that was scanned out of range.