I am trying to develop a proximity logger.
Basically I have 2 mobile devices (microcontrollers), when the devices are within a 1-2 meter from each other, they should exchange IDs (a simple integer value or short string). The ID should then be logged (so some serial connection). When the devices loose communication, it should again be logged (just interrupt the microcontroller).
I've done some research, effectively I'm trying do NFC but for a longer range and small data transfer.
Any suggestions on hardware I could use, or alternative research I could look into?