Brightkite for the iPhone

Brightkite for the iPhone from Brightkite on Vimeo.

From the site:
Brightkite for the iPhone puts the most popular features of right into the palm of your hand. Features include:

*Auto geo-location including Place Snapping and Pick a Place
*Notifications (nearby friends, posts, friend requests, comments & mentions)
*Posting photos and notes to locations
*Nearby people and activity feed
*Friends lists and activity feed
*People, places and posts search
*Threaded messaging
*Profile streams
*Place steams
*Commenting on posts

Get an invite:

About Brightkite:
Brightkite makes it easy to meet people based on the places you go. In real-time, you can browse profiles of people around you, see what your friends are up to, post photos and notes to places, all while maintaining comprehensive control over your privacy.