I've been hearing about location based services being the next big thing for many years.
Now that I'm playing with Twinkle on the iPhone I'm starting to get it.
You can see, and therefore make contact with, people who are close to you. It can be a little spooky and of course you need to be aware that bad people might be looking for people to stalk close by, but it certainly shows a new way to hook up with interesting folks who you might want to hook up with in "meatspace".
I can see a ton of applications for this already.
Oh, and to take screen shots on iPhone 2, hold down the "home" button and click the top button. The screen flashes and the picture goes in your camera reel as a PNG.