[–] thantik 0 points 1 points (+1|-0) ago 

Just a heads up, I tested this the other day -- you can spoof an SMS to reply "YES" to their little opt-in thing, and you can track anyone's phone number that way. I tested this on my own phone, without ever sending a reply to their opt-in. While your target will obviously get an SMS alerting them to the fact that they're being tracked, there's nothing you can really do to stop it except quickly reply "STOP". Which a lot of people aren't going to do quickly enough for that first location ping to go through.