Balloons! for the iPhone (and iPod touch) made me smile. It's like Distant Shore, but more personal and fun. Don't get me wrong, I love Distant Shore, but Balloons! reminds me of being a kid and tying a message and photo to a balloon to send up into the stratosphere. Plus, you get a real sense of community. It's just plain fun to pick up a virtual balloon supposedly drifting past you. To see what I mean, check out the video. But if you ever tied a note to a balloon and let it go, that's what this does. Except now you get to catch other balloons, have conversations and attach photos all from your iPhone.
Unfortunately Balloons! isn't in the store yet, but from the build I saw looks pretty close to being ready. The Balloons devs are looking for beta testers, which you can apply for here.