You might look into Life360. My wife and I use it in our auto travels. We use Verizon and as stated pretty good network coverage but not 100%. We travel in northern Michigan and the U.P. There are some dead zones. It does, obviously, require GPS/location be turned on. You might want an auxiliary battery along just in case. For cycling I use Strava's Beacon Text. It's sent to my wife's phone when I ride so she can track me.