My gay guy friend has an app on his Hero where gay/bi guys post their profile & their location automatically updates w/ gps. For example, my friend does a search according the certain filters he sets. Say he wants to do a search for gay men 25-35 who are up to 10 miles away. He does the search, & then a bunch of thumbnail profiles appear w/ the pic, screenname, age, & location of everyone who fits his search.
I think that's pretty dang rad! I'd love to have an app like that. Like, if I'm out @ a busy shopping center I could do a search & find a cute chick to treat to coffee.
I've also heard of "gaydar" apps that make the phone vibrate when you're w/in a certain distance of someone else who is logged into the app. That would be fun, too :).