ViveNerd

An interesting idea... since the Focus is an Android device, you should be able to use bluetooth like on any Android phone, but since the direct access to bluetooth is not provided in the UI, you might look into controlling bluetrooth via a plugin such as this one if you are developing on top of Unity. If not, you can find code examples for bluetooth programming in the net. Once you got this solved, you could use a bluetooth controller such as the PS4 controller. Just my 5 cents worth...