Zoom B3 works with my iPad. I asked this before in this thread, and finally got around to testing this today.
You will need a
powered usb hub and a camera connection kit usb adapter. I am using this usb hub, but I imagine others will work:
http://www.amazon.com/Macally-Mini-7-Port-Adapter-TriHub7/dp/B001DBF07S
I tested it with Garageband and Ampkit, but not Amplitube.
I used the Audio Recorder in Garageband, and you need to make sure you have monitoring turned on. Background audio in Garageband doesn't seem to work, but I think that's an issue with Garageband in IOS rather than the B3.
Ampkit worked great, and allowed me to use background audio while jamming with Capo or an iTunes song. I used the amp sims on the B3, so I turned the amp and cab sims off in Ampkit. I suppose you could use the amp sims on the B3 and use the stomps in Ampkit, or vice versa.
You might need to adjust the input/output levels on both the B3 and your iPad app of choice.
This is an easy way to record to the iPad or just practice to jam tracks with the B3.
I tried the same method with an iPhone 4s but got the "USB device not supported" message upon plugging in the usb dongle with the B3 attached.
If anyone would like, I can test it with Amplitube, JamUp, and Everyday Looper in the next day or two.