Their app shows a map which has pins representing your friends and how close they are to you. You can text them, call them, or even just leave a message on the loopt service for her. If she agrees to meet with you for lunch, you can get directions to her location with one click. It will be FREE on the iPhone App Store at launch. Seems neat, and mirrors apps we've seen already on phones like Helio's Ocean.
Next up is Loopt, being demoed by Sam Altman. It's a social networking tool with location-based services. (I can't see, but I think the guy is wearing two collared shirts with one of the collars popped.)