Share 'For the purposes of grinding.'

So, I'm working on 2 final projects wherein I'm using tags or small devices for tracking/security. Originally the plan was for RFID but apparently its been done before (not surprising, it is NYU) but no one's really dabbled in GPS tags or tracking, and I've got a few ideas I could shift that way. So I figured this was an excellent source of techies, does anyone know of a GPS service that works…