If Google ever makes hardware to go along with its rumored game streaming service, you might have an idea as to how it will work. Yanko Design has spotted a recently published Google patent application for an internet-connected game controller that would be independent of any one host device. It could receive notifications for chat, play invitations and other content, and could launch the relevant app on any relevant device -- you could jump into a multiplayer match on your tablet if the TV is in use, for instance.
The gamepad could also store your account and host device settings (like brightness and volume), not just familiar hardware options like game-specific button bindings and general gamepad settings. You could visit a friend and instantly pick up where you left off.
Google originally filed the patent in 2014 (hence the Android KitKat-era "home" and "menu" buttons), and it's quick to warn that the image you see above isn't likely to be representative of any finished product, if there is one. Still, this may offer insight into how Google would approach an expansion of Project Stream into a full-fledged service. Rather than sell a whole console, it would just need a cloud-aware gamepad that can talk to the devices you already have.