Apple has filed a patent for a so-called “smart ring” with biometric sensors that could potentially be used for authentication.The proposed smart ring features a microphone, raising the potential for voice biometrics, and heartbeat sensors that could validate ECG.Similar to its Apple Watch, the device would have built-in vibrations to let the wearer know that something has happened.It also suggest that the ring could uses built-in accelerometer and gyroscope modules to determine what you're writing by following the motion of your hand.In an example of voice authentication, the patent describes a method by which one user authorizes a money transfer to another ring user simply by shaking hands. In this particular case voice commands are used to authorize the transaction, with a user saying, “By shaking hands with Steve I agree to give him $20.” The technique can also be used to pass along messages and other protected digital data.Apple's ring computing platform patent application was first filed for in April 2015 and credits Marcos Regis Vescovi and Marcel van Os.