One added problem will come from directionality of the RF signal from and o the handset, especially when the device is being held in the hand, and near the body(which has natural capacitive effects) that will impede the RF signals.

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Again, you have to deal with signal issues in high-RF noise environments, deal with materials issues acting as RF shields (like in many computer rooms or anything with lots of metal in it), and you have to balance the convenience with the somewhat-increased security risk.

FORBES: Got Wires?

V. (NASDAQ: NXPI) provides High Performance Mixed Signal and Standard Product solutions that leverage its leading RF, Analog, Power Management, Interface, Security and Digital Processing expertise.

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Embedded inside it is a batteryless RF switch, and the way it works is that upon the release of the spring mechanism inside, a tiny bit of power is generated for the 2.4GHz RF transmission ( ZigBee compatible), and whatever device is connected to the RF control outlet on the other end will receive the on or off signal.

ENGADGET: Mitsumi exhibits micro-vibration power generator and batteryless RF switch (video)