Comment Whats wrong with (Score 1) 383
a finger ring (or better yet an implant) with a unique RFID chip in it.
If the chip is not in close proximity to the computer keyboard, the compuiter immediately lockscreens.
An API to read the unique code of the user's chip would be avaiable to online apps too, so websites can use the same system to authenticate.
For extra security, the ring/implant could also continuously detect the wearer's presence and life, possibly with biometrics as simple as confirming the users pulse. If the signal is disrupted the implant can assume it is no longer secure until its reauthenticated.