I have an irrigation valve that turns the water on and off for the garden. It talks to the app via Bluetooth, and I’ve found that my phone has to be at least 3m away from it or it won’t connect. Any closer and the signal must overload it to the point where it can’t interpret it. The first one I bought, I took back to the store and swapped it for another before I figured out what the problem was.

I’m sure it’s a bad design on the valve’s Bluetooth implementation, but nevertheless, it exists.