Using an iPad I can get some great guitar tones, do looping, run vocal effects, do my mixing and control everything with a MIDI floorboard - it's awesome for solo and due artists who don't have access to a full band; simply plug into the iPad and run it out to the front of house system.
What we don't have is drums.
What I'd like to see is an app similar to EZ Drummer on the iPad but with some influences from Beat Buddy (see http://mybeatbuddy.com/) where I could map a MIDI floorboard to the drum patches. Each patch would have a Transition; this is a MIDI part that would play whilst you hold the button down. When you release, the Main Loop would play. Tap the button to play a fill for that patch. So imagine if you will the EZ Drummer UI but with this at the bottom (each word is a placeholder where you can drag and drop a midi clip)....
Intro
A---------------------B---------------------C---------------------D
Transition-----------Transition------------Transition-----------Transition
Main Loop--------- Main Loop---------- Main Loop----------Main Loop
Fill 1----------------- Fill 1----------------- Fill 1----------------- Fill 1
Fill 2----------------- Fill 2----------------- Fill 2----------------- Fill 2
Fill 3----------------- Fill 3----------------- Fill 3----------------- Fill 3
Outro
So using an interface similar to EZ Drummer, I could set my tempo, choose my kit, use the 'tap to find' or browser to find the beats and drag those clips into the patch area at the bottom to build my song. Then I could save it as a song preset.
This also means I could purchase new kits, new MIDI libraries and also pre-made songs (a bank with pre-configured patches).