UHF RFID communication or something similair
ISO15693 13.56Mhz RFID tags cover a range up to 1.5 meters if you have a big antenna. That would be a cheap solution.

One more option would be to use some cheap 433Mhz transceiver chip and run it at low power to limit the range. 

Also Bluetooth Low Engery may be used. Some transceiver allow you to measure the field-strength. This can be used to approximate the distance between the two devices.