Feature Request: Add support for head gestures

[ymoliner]

Like it says in the title add support for head gestures and to be able to customize them to do different actions.

[hiSandog]

For head gestures, the useful first step is probably an acceptance list: which gestures are supported, which device/API reports them, and which app actions they can map to. It would also help to define what happens when the connected device does not expose gesture events, so the settings UI can avoid showing controls that cannot work on the current hardware.