I used to use this program awhile back ago when I had my Nextel phones. It's called mologogo and it basically works out like dodgeball.com in a way, except it just kinda shows you by GPS where your friends are.... I don't know who all would have interest in it, but I liked what it did. I'd put the cab up, but there is a license agreement and you have to sign up. Check it out... btw, it is free as long as you have a data plan.
www.mologogo.com
Check it out.
and no... I don't work for the site.