Loopt allows you to share your mobile location with others and you to view theirs on your mobile phone (on a nice map too). You can create a profile - with privacy settings, set-up events and invite people.
It's only available on Boost Mobile in the US, but I'm sure they're hammering on all the other operators' doors. Their site doesn't indicate the costs of the service though.
The UK has seen the launch of several of these services since 2003, when the operators made their subscribers' location information available to third parties:
- Locate Mobiles
- KidsOK (out of business)
- Disney has also pulled back from launching its service which included child tracking functionality.
The reasons for the failure are three-fold:
- the commercial cost each location look-up
- the accuracy of the service using cell-id or even triangulation
- the regulatory issues surrounding the service makes implementation very clumsy. (Imagine the public outcry if a paediophile tracked a child's location - it just doesn't bear thinking about).
The only service that has made some inroads are 'where am I?' and 'find my nearest' - both of which are entirely selfish & don't have a social angle (and best offered by the operator directly).
Update (October 26th):
Nokia have released their all singin', all dancin' N95 with GPS and a mapping application. Nokia have also licensed GPS software from Trimble for their handsets.