It's a little 1984-ish, but via your cellphone people you chose to track you, can track you.
I don't think anyone can really tell if I'm at 7-11 or Popeye's, just that I'm in the general vicinity. ....and it's not like I have a ton of people who I'm following or allowing them to follow me. As you can see from the map below, I've got bi-coastal coverage (thanks Moby, thanks Brad).
Now, if you want to get really really personal, just team up loopt with my new most favourite (yet untested) iPhone application
Yes - use loopt to find which bathroom I might need to use at a moment's notice. CREEPY.
Song by: the Bangles