Bluetooth Transponder Chip

Inspired by pottedstu's comment on 'Bluetooth Wristwatch': "The power consumption for bluetooth is not negligible. I don't think the battery life would be too great. But if you can live with that, fair enough." A fair point.

I'm a firm believer that technology has to be practical before it can be adopted and a watch that needs charging up overnight just so that can set its time when you walk past a clock is not going to catch on.

Enter the bluetooth transponder chip. This would be a very short range bluetooth device that would power itself from the radio signal received by the base station and would feebly transmit its terse reply. The base station would probably have to have to be engineered to support unpowered transponders with a very effective antenna and sensitive circuitry to detect and understand the neccessarily low powered responses.

The chips would be embedded in other devices: watches, thermometers, secutity passes which would gain on battery life by not having to power the bluetooth transmitter.

Further devices could be developed with low power needs where the bluetooth chip would soak power out of all bluetooth (and possibly other radio signals) powering the whole device. This could lead to a range of short range radio devices that would not need batteries: Bluetooth socks (not only capable of locating their other half but of telling you when they were last washed), Bluetooth solar radiation sensing necklace/sunglasses/beachtowel that tells you (via your organiser) not only when you've had too much sun but when the Germans are about to nab the sunbeds, etc etc etc, yada yada yada, bla bla bla.