Just downloaded and opened the link in a version of both CS3 and an older version photoshop (7.0). It's gorgeous, and exactly what you're looking for. It comes with everything sized to fit their included iPhone template, has customizable text for all incoming transmissions, and has what are essentially drag and drop buttons. This is way more comprehensive than anything that I would have thought up, and I'm going to recommend this so highly. All you need to do is change your character's wallpaper.