form options: personal space

so does this personal space contraption need to be worn around the waist? what about wristbands each with an ultrasonic rangefinder in them – then, both giving the wearer control by stretching the arms, but also automatically detecting what’s “too close” and triggering the response. but is that problematic because as you move your arms, other objects may come in the way of the rangefinder and activate it intermittantly, in motion from one position to the next, or something? or even perhaps something you are holding?

no matter how i end up doing it, i should remember to add an on off switch.