Smart wearable devices and methods are disclosed for providing feedback for optimal placement of the wearable device. This includes systems and methods to lock or unlock a wearable device and/or notify external wearable/non-wearable devices depending on the states of the wearer by sending notification or providing feedback if mispositioned or repositioned on the wearer. A system and method are disclosed for providing a user indication of proper placement of a wearable device by providing feedback based on acquired bio-signal quality. In one embodiment, bio-signal quality is acquired by comparing a computed signal to noise ratio to that of an expected signal.