The bbc iPlayer does essentially this now. It creates a short one time code and you type it into a logged in account to activate the smart device. Of course, w

The bbc iPlayer does essentially this now. It creates a short one time code and you type it into a logged in account to activate the smart device. Of course, when you only have one logged in device and it's tied to a different room, it's mildly irritating, but you only do it once.