I use the Tunes Remote app to allow me to use one iOS device to remotely control another one used as a media player. The player might be connected to a TV or stereo system. It works pretty well - pretty similar to using Apple's Remote app on my iPhone to control my Apple TV at home.
Many thanks for your reply. I actually meant largely with regards to texting. If I'm on my iPad and I receive a text on my iPhone, is there a way I can control the screen on my iPhone to reply to the text on my iPad?