I've been trying to figure out the cheapest way to do a head tracking FPV on a 3d printed quad copter. Put an old android phone on gimbal servos on the copter then use google cardboard for the head mounted display and head tracker?
then for a bonus, use a 3d puck mouse normally used for CAD as controls for the copter. So it will hover when you let go, up when you pull up, etc. for zero training for the user.