We would like an iPhone app (and later, a Droid app) that is quite simple.
Once the app is launched, the camera on the phone starts up, and you can take a photo in the usual way. Once the picture is taken, the user can then tap on the frozen image and add a predefined graphic from a choice of a few and overlay this graphic on the photo that is taken. Ideally, you could position this overlay anywhere on the picture you just took.
Once this is done, the user can then upload this composite image to Twitter, Facebook, etc.. It would be nice to be able to add tags to the image before uploading it..