Akai Synthstation iPhone

Does anyone have any experience using their iPhone as an interface with a controller like the Akai Synthstation in services? I would like to use it mostly for pad and electric piano sounds. Set it up with another keyboard for actual piano sounds. Any thoughts?

I have the line 6 mobile in, it works great! I play it through my phone speaker, headphones or run an audio to quarter inch adapter into my amp! It sounds very nice through my amp. I think it has the highest signal to noise ratio on the market. It's $80 and the app is free. I only use it for guitar, but it works with other apps like GarageBand, it may work for you if there's an app for what you're going for. The only thing sketchy is the boost switch. I have to touch it on the screen. It doesn't flip on consistently, so even if you have one second before a solo to poke it, I have trouble doing it more than 60%-75%, ie nothing happens.