As an additional safety feature, I want to be able to shut down a 30mW laser diode if anyone gets close to it. One thought I had was that technicians approaching the device could set their cell phone to pairing mode If a Bluetooth module could detect the presence of a pairing request and signal the Arduino, that should work. However, I can find only information on using Arduino with an already-paired Bluetooth Serial device. Anyone know if a Bluetooth module that can be used this way exists? Thanks.
(I will probably also implement remote shutdown using a keyfob type RC device like the 315MHz transmitter/receiver sold by Adafruit, but it would be nice to have something less likely to be lost as a backup, even though Bluetooth's range is so much less.)