I remember Loopt being one of the first apps out on the App Store, back when the iPhone's platform was first released. A couple of years ago, location-based social networking was still pretty new (most cell phones didn't yet know exactly where they were, after all), and Loopt was one of the most advanced ways to do it at the time. Now, while services like Twitter and Facebook work on their own location sharing features, Loopt is updating to version 4.0 and aiming to, once again, try and take the vanguard.
The app has been redesigned, and it seems to be set up around persistent social location sharing -- you can not only share your location constantly, but you can also instantly see where friends and family are. You can also use the "Ping" feature (unrelated, of course) to send texts, and you'll get a message back from your friend about where they are when those are opened. And Loopt continues to offer local "rewards," which are free offers and deals based on where you happen to be.
It's all very interesting -- while, of course, there are the usual privacy concerns as with any location-based app (one of the reasons I don't really use any services like this regularly), the new Loopt seems to really take advantage of mobile platforms like iOS to keep an almost constant connection with your social circle. The app's been around and updated since the App Store first opened, so we'll have to see how this new direction works out. Look for version 4.0 sometime later on today.