I'm using a Yamaha Motif XF8. Has a great weighted keyboard and an awesome voice library.
I have a tiny wifi adapter plugged into the usb of the Motif, which allows me to connect to my iPad 3 wirelessly.
As there are several wonderful Yamaha apps available in the App Store, which are very useful for us keyboard musicians.
I hope you find an app which works well for you too. Smile