I'm sure you are thinking get him a phone so he can call you...but Oxford Houses aren't jails, he can go to a payphone and call collect in an emergency. Otherwise, he could write letters to communicate. If he wants a cell phone so badly, he can get one himself when he starts working and saves up money for it. Also that will be more meaningful if he's done it himself.
There is no way to control him calling the AGF. Chances are, since they didn't officially "break up" that is exactly what he would do with the cell phone. Also he is just going to Oxford House for recovery right? No rehab or anything before? He's proven nothing as of yet. Just because you check in doesn't mean anything until ACTIONS start speaking louder than words. Making it easier on him isn't the best path. My AH's counselor said that sometimes it's the best when they really have to struggle so they learn they never want to come down this road again.