As you can see from my question on h/w recommendations, I am trying to design an evacuation system for a chemical factory.
That requires knowing which room each employee is in at any given time. I can handle the system to track the employees, but have been looking for a long time for a durable wearable with long battery life for each employee to wear or carry.
I had considered Android 'phone, but theymight be too expensive/bulky/fragile/short battery life.
A Raspberry Pi Zero W is cheap, but also quite large, needs a casing and I am unsure about battery life.
Passive RFID might not have the range, and active requires battery.
The AdaFruit Flora BLE looks interesting, but I can't find data about its battery life.
The I had an epiphany when I looked at my wrist and saw the cheap fitness tracker on my wrist. It's a Xiaomi Mi Band 3 which I got free with my last 'phone.
I am charging it about once every 3 weeks, although I currently do not turn BT. I will need to calibrate that, although reviews give it 7 days of heavy usage.
So - finally - to the question: how can I detect transmissions from the device? If they are frequent enough (say, more than once per minute), then it doesn't matter what the signal is, so long as I can get a MAC address out of it and use that to locate the device.