Currently on NZ3 - $30/device, one device at a time - you can switch between devices although it's kinda cumbersome. The portal displays a six character code that you have to enter on your new device - I'd imagine you'd be out of luck if for example your laptop ran out of battery and you didn't have a charger handy.

I prefer the UA approach where wifi is attached to your FF account and you can choose which device has access from there.