II use the HC-12 communication device exclusively for all my remote control projects, having used and tested "all the others". The HC-12 is so simple to use. It only needs two wires (plus power and ground) connected to Tx and Rx of an MCU. Send data to the HC-12 and it puts it into a buffer and streams it out without any extra coding. Other devices need a page of finnagling code to make things work.
So, it made sense to make a test device that I could use to verify operational status of the HC-12, because it can get quite finicky and has programmable parameters that require perusal once in awhile. Sometimes I have to change channel when I suspect that there may be interference with other devices in the home.
I made a transmitter test bed on a 4x4 inch square piece of bass wood and also a receiver. Shown here is the transmitter, using an Arduino Nano for the MCU, a joystick for data provider, and an LCD to see what I'm sending out on the HC-12 located at top right.