Record iPhone 4 music apps on to iPad 2?

[dtower]

I would like to connect my iPhone 4 to my iPad 2 so I can play iPhone music apps to the iPad (like playing an instrument) and record the music on the iPad. Any one know how to do this? I have Harmonicdog Multitrack DAW and StudioMini XL installed on the iPad now. What kind of cabling/interface would I need to connect iPhone to IPad?