Most Bluetooth keyboards can pair with only one device at a time, be it a Mac, iPhone or iPad but this Apple keyboard accessory can pair with up to four Bluetooth devices at the same time. Priced at 100 dollars, it lets you switch to your preferred device using four quick function buttons placed over the numpad. 
Official Mac Bluetooth does not feature a dedicated numpad but this one does. So those who key in a lot of numbers will be very happy. In the box, you will get Kanex MultiSync Aluminum Mac Keyboard, Quick Start Guide and 2 AAA batteries.
It is compatible with iPad (all models), iPad Mini (all models), iPad Air (all models), iPhone (all models) and Apple TV (2nd and 3rd) Generation. On iOS devices, it requires v5 and above and on Mac OS X, it requires Mac OS10.6 and above.