Look at the AC-7 Core HD. It is about the best on the market. Saitara Software also makes other versions, plus a really nice iPad MIDI wireless keyboard.
the AC-7 Core HD is a great iPad controller for Logic. There are quite a few iPad controller on the market. IpTouch also looks very nice.
I'm a fan of TouchOSC ([url]http://hexler.net/software/touchosc[/url])
It has a different look to it, and its very customizable. There's a bunch of templates for the different DAWs (Logic, Ableton, ProTools, Reaper etc...)
You can also control your plugin parameters with TouchOSC.
Been using ipTouch for a couple of week now. Pretty darn useful, even for a newb like moi. Quick hook up with my MBP and plenty of straight ahead control surfaces with a more than a modicum of customizability. I love the EQ function and fine tuning capabilities that gives. I know there's much more here to discover.