Altitude - View & Share for iPhone (free) is an interesting little app that reports on your current altitude. Once launched, the app displays your altitude in meters or feet over a landscape photo meant to represent your surroundings. With a tap, you can share this information with family or friends via Facebook or Twitter.
That's great, but what if you want to use your own photo? An in-app purchase (US$0.99) unlocks this feature. Once bought, you can save a custom image with altitude information intact to your iPhone's camera roll.
The option of using your own photo is a nice touch. Still, I wish I could share via email from within the app. As it is, you have to make a trip to your camera roll. That seems a weakness in an app that bills itself as a sharing solution. I also wish I could choose an existing photo. Altitude requires you to shoot a new one. (The author of the software says that function is in the app. I didn't find the control obvious, but it is there.)
Finally, the built-in photos slowly pan left and right, while custom pictures remain static.