...As long as it's Core MIDI-compatible, the answer is yes! This includes old MIDI hardware, as long as you have an appropriate third-party adaptor (like the iRig MIDI, etc.)
You can find a list of devices that are known to be Core MIDI-compatible (and those that aren't) here: http://iosmidi.com/devices/
Yamaha is one of my favorite companies. Anything I've ever had from Yamaha has been durable, long lasting, and high quality. With that said, it pains me to reveal that I will have a few negative things to say about this keyboard, in addition to the positive things I have to say.
Very unlikely, @saichele - I'd rather not encourage Korg's folly! IMHO WIST is Korg's attempt to create their own version of MIDI clock sync. MIDI clock sync is well-established, works well, and is very compatible. Korg are doing nothing but damaging the music industry by reinventing it, and I'd rather not support it. 'nuff said.
Michael, love your product although I haven't had much time to explore. Have you tried using loopy with the midi bridge app? I use it play sounds from various apps with the interface of other apps. Example, would be playing garage band sounds through Geo Synth. It also connects midi hardware. Wondering if this would work to connect Loopy with other apps. I don't know if it gives recording functionality though, but may be worth a try.
Anyone know if the http://www.tech21nyc.com/products/effects/midimoose.html is midi compliant or know of a midi foot controller that is that is also battery powered? Was gonna go with the fcb 1010 but the wall plugin kills it for me.