Real-Time GPS Tracker Not sure if there is a track back function but there are loads of these types of apps and 1 of them must have it...

https://play.google.com/store/apps/details?id=com.greenalp.RealtimeTracker&hl=en

Show your exact location to your family and friends on Google Maps for free. This is more than a GPS Tracker, this is real live tracking for location sharing.
You can also see your friends' location but they need to run this app.