In the UK, you can track anyone's location to their mobile phone, for 10p each time you check on a website. It gives you the current live location of the phone on a map like Google maps, with no charge other than the 10p cost of each visit to the website, as far as I know.

I investigated it thinking of my own flying, (and also my teenage daughters locations!) and after checking with O2, find that this service is not allowed in Ireland.... Probably not a bad thing in many ways! Would certainly be handy though.

Oisin