Email N Walk is an interesting email client for the iPhone.
When you first open the app, you are given a subject line and a message box. What makes this email application unique is that it displays your camera in the background. So, instead of typing on a plain white background, you are given transparent boxes with the camera providing a live feed of what is in front of you. Tapping the "Send" button on the keyboard will direct you to the default email application, where you can fill the "to" address or any other information you would like.
Originally, this application began as a practical joke, but soon gained popularity as time went on. The uses for this app could very well be boundless. If you want to watch TV while typing an important email, you can now do both. Or say you want to check somebody out without appearing to be a stalker; simply pull up this application and you'll look as if you are an important kind of guy, but in all actuality you are watching the person from your camera. As silly as I may be sounding, these are valid uses for this app. Though I do have a complaint: instead of using the transparent keyboard available for the developers to program with, they opted for the "gray" keyboard, which limits on visibility; Though this just may be due to hardware limitations. As this app is only 99 cents, it may be worth your money to check this app out.