Here are quotes from Chuck Lawton's review of the iRig KEYS from Wired.com:
"iRig KEYS is a 37-key mini keyboard and MIDI controller. It works as a Core MIDI device for iOS and a USB class compliant for seamless use with any app or software which supports MIDI devices on both Mac and PC."
"I tried out the iRig KEYS on both my iPad Mini and Mac. Using the Lightning adapter worked great and the Garageband App detected the keyboard, no problem. I pulled up a previous project and started playing with the pianos, organs and other MIDI instruments Garageband offers. It was a truly plug and play experience that let me focus on making music and, again, brought out the fun that Garageband is capable of."
"IK Multimedia also publishes two great apps that serve as companions for iRig KEYS. The first is SampleTank which contains over 500 instruments over 16 categories including drum samplers, a wide range of electronic and orchestral instruments. SampleTank is free with various instrument packs unlockable with in-app purchases. The second app is the iGrand Piano, which has the most faithful piano samples I’ve ever heard on iOS. With pianos ranging from Classical and Grand Pianos to various uprights and even a fun Saloon piano, the app offers an incredible amount of range. Each piano is customizable with options for adjusting volume, ambience, and lid position and the automatic release of keys when not using an expression pedal are phenomenal. Both apps are compatible with the iRig KEYS along with a dedicated iOS-compatible MIDI adapter called the iRig MIDI, so you can bring your own MIDI keyboard if you’d like."
"Overall, I feel that IK Multimedia has a home run on their hands with the iRig KEYS and the supporting apps they’ve created. They’re smartly designed, work well together and they sound incredible. Any keyboardist who’s been jealous of all of the products out there catering to their guitarist friends finally have an equally portable solution for practicing, writing and performing."
"Extremely portable and feature rich with velocity-sensitive mini keys and convenient buttons to activate features in equally rich first-party apps. Flexible use with both iOS and Mac or PC."