You can connect with up to three devices and then easily toggle between them with the button. It is rather ironic that my Nokia Lumia 1520 Windows Phone doesn't support Bluetooth keyboard connections.
I connected and tested the keyboard with a Surface Pro 3, Huawei Ascend Mate 7, and Apple iPhone 6 Plus. The keyboard has a toggle in the upper right to let you switch between Windows, Android, and iOS. It is much more portable, has rechargeable batteries that last up to six months, and is a higher quality product. However, after testing out the new Microsoft Universal Mobile keyboard I would spend the extra $30, available now for $79.95, for this accessory instead. I tested out the new Logitech K480 Multi-Device keyboard early last month and found it to be a decent option at $50. Let's take a closer look at the accessories centered around my Surface Pro 3. I used to go upstairs to use my wife's iMac for heavy duty tasks, but haven't touched the iMac for at least a month. This new setup allows me to function with a dual display setup and seriously increase my productivity. I have since expanded that a bit with the Surface Pro 3 Docking Station, brand new (released yesterday) Universal Mobile keyboard, and a Dell S2240T touch monitor. Back in July I wrote about my home office being powered by a Surface Pro 3.