OPPO has had a new patent for potential next-gen wearables granted in its native China. It is intended to allow the accessories in question to authenticate the user by reading their veins rather than their fingerprints or faces. This form of biometric recognition could thus be added to a future Band or Watch from this OEM.
https://www.notebookcheck.net/OPPO-patents-wearables-that-unlock-through-user-vein-scanning.555545.0.html