Google Latitude is cool — you can see where someone is at any given moment (as long as the phone running it is on, that is) but it also completely weirds me out.
I don't mind that my boyfriend knows where I am at all times with Latitude (which can be shared as the exact location or just the city), but it's weird. So weird that I'm cool with having it installed, but I refuse to check out where he is (unless there's an emergency). It makes me feel like a stalker. A connected stalker, but still.
The app Loopt sort of does the same thing — keeps location tabs on your friends and lets you know when they're nearby — awesome if you want to run into someone, awful if you're trying to avoid them.
The Google blog announced today that Latitude can also be shared with your non Latitude friends in a variety of ways, so yaaaay. . . or nay?