This morning at their Mobile World Congress Microsoft announced a new Bluetooth foldable keyboard that will work with an iPad, iPhone, Android and Windows and Windows Phone (with update 2). The keyboard looks very much like the Surface Type Cover with the addition of it being foldable in the middle. I love the Surface keyboard so I think this could be a great keyboard especially as it will work with all my devices.
It has a built in re-chargeable battery, is just 11.5mm thin, it is spill resistant and has a one-touch device switching button making it easy to switch between devices. The recommended US price is $99.95 and I expect the UK price is going to just under £100 so it is not a cheap device but if it is like the Surface Type keyboard then it will be a very effective keyboard. It could be the one keyboard you need for all your mobile devices.