The Gibson "robot" guitars have this "pot tuner" on board. It goes one step further in that if you have the robot engaged it actually turns the tuning peg for you if it detects the string you are plucking is out of tune. Howver you can disable the auto feature and just use the pot itself as a tuner. It is pretty cool.
I guess the robot guitars never caught on as I saw these when i was dropping off my es-135 at the luthiers and someone else had just dropped off 3 brand new gibson les paul robots that were bought for a ridiculous clearance price at sam ash NYC. The guy was telling me the sam ash people were saying they were having trouble giving them away!
I dont know if I would want those robot tuners, but it was pretty damn cool to watch, The luthier was checking the robot tuner accuracy against his strobe tuner and it wasnt bad.
.......................................................have you heard the one about the yellow dog?