As part of a home automation setup I want to make a simple switch that is activated when I hang up my keys to announce to the system that I’m home. I don’t want to have to run wires to my key holder so I’m looking for something that could wirelessly transmit the state of a switch and could be run off of a coin cell. This is very low bandwidth and only needs to transmit about 20 feet. Any suggestions on the best wireless technology to use?
A modified keyfob transmitter might be the easiest way to go: https://www.adafruit.com/products/1095