None of this is new and Johnny isn't the only one doing tracking. I hope Apple's patent is rejected due to existing work but given the patent office's record as of late... I'd imagine Apple would be fine with that too so they can incorporate this into their products w/o strings. Its odd that companies need to apply for stupid patents just so they don't get sued by trolls down the road.
BTW2, there are decades of existing products that use electromagnetic, vision, IR, magnetometer and acoustic technologies for tracking.
BTW3, Apple's patent is attempting to patent fish-tank VR which itself has decades of existing work.