I slapped this project together on a Sunday afternoon with parts I had on hand for my son’s annual Boy Scout rocket launch meeting. I’m using the Microbit’s radio function to allow one bit to send a launch command to another which then uses the I2C function to close a SparkFun Qwiic relay shorting the 9V line and lighting the engine. This all worked surprisingly well and the only problem I had was that the Microbit cannot tolerate the 3.7v provided by the single cell lipo batteries I was using. I added a 3.3V LDO and a Schottky diode for good measure and called it good.