It would be possible to use an RFID chip e.g. To be attached to a laptop and programmed via the app, e.g. Alarm goes off on the smartphone if the laptop is more than e.g. 1.5 meters away? Would it be possible to set the sensitivity via mobile phone?
No, that's not possible as you imagine it to be.
But there are such Bluetooth devices
So would that only be possible via Bluetooth? Or are there still alternatives?
How big are the transmitters / receivers and where are they priced? Can someone tell me more about this?