Good luck – I think your teens are going to chafe at that. I can imagine the geo-fence option for 10 year-olds, but at 12 and 14, your kids probably won’t accept a Migo phone (it’s pretty childish looking) and they’ll figure out that they can just turn the phone off. If the phone is off, the Chaperone service won’t work.

See details in this write-up:
http://www.kidswireless.com/articles/verizon-wireless-chaperone/