I had this idea several years ago, and assumed someone else would eventually make and market it, but in 2019 I still haven't heard of anything like it, so I thought it about time to mention it on these forums.
The idea is pretty simple, both the vive and rift hand trackers use a ring with several points on them to position it in 3D space. What if those rings weren't attached to a hand held controller but instead went around the forearm like a bracer, they'd have to be hard plastic with an elastic sleeve inside so that one size fits all. Integrated into the rings plastic ring are leap motion style cameras, pointing down towards the hands.
Essentially you'd get unoccluded, high precision hand tracking completely independent of the HMD.
ideally the leap motion software would run on a small CPU inside the bracers and only transmit relative coordinates, reducing the comms to a level that works wirelessly, similar to how vive hand trackers do it.
Does anyone know of anything like this out there already, or messed with creating such a system?