Change Friend's Android wallpaper
My wife and I are in different parts of the country right now and we have found this to be a great, subtle, way to let the other person know we are thinking about them! I can take a funny picture of the dog and set it to her wallpaper! For the email address, set it to the person who you are allowing to change your wallpaper. So in my case, it is set to my wife's email.