The HOPE conference was last weekend and [Nathan] spent some time with fellow members of Makers Local 256 developing this badge proximity sensor. They took one of the HOPE badges, which have a radio on board for the tracking network, and wrote code for its MSP430 to detect other badges nearby. It uses a Geiger counter they brought with them as an enclosure, re-purposing the analog gauge to reflect the level of active radio signals in the area. You’ll find their demo clip embedded after the break.
If you managed to get your hands on one of these badges, don’t be shy about sharing your hacks. We want to see them.