Neotropolis The Making of the Railgun Trackers

The speaker, a software engineer, describes the railgun props used in a live-action roleplay game at Neotropolis, a cyberpunk festival in the Mojave Desert. Each prop carried a Bluetooth Low Energy beacon that simply broadcast its discovery packets, and game hunters used handheld trackers to locate them.

The tracker reads received signal strength to estimate distance. It runs on a stock M5Stack Core 2 with the Arduino BLE stack, and the operator programs in the target's MAC address. The display moves through a scale from ice cold to red hot as the target gets closer. The speaker demonstrated this in the hall by carrying a beacon away from the tracker. He compared this with multi-receiver triangulation, which is more precise but was not needed for the game. He also noted that a connected device stops advertising, which limits the method.

The second half turns to privacy. The same approach could follow any nearby phone with Bluetooth on, and he cited camera networks that collect device addresses alongside license plates as a way to link an address to a person. MAC address randomization would help but is not yet common. His practical advice was to keep Bluetooth off when it is not in use.