The BBC Microbit includes a great feature allowing a simple radio connection between 2 MBits to exchange data.
Using this feature in conjunction with a low cost Ultrasonic 'sonar' component shows how a simple, yet powerful project can be created, where one microbit operates the sonar and reports back to the other 'remote' microbit.
The ultrasonic sensor is triggered to send out regular pulses. If an echo is received within a programmed distance, the detecting microbit will note this as movement and alert the remote microbit, which displays an icon on it's screen.
We found that the microbits could communicate effectively in adjacent rooms and at a distance of over 30 feet apart.
Download the attached PDF file for details of the circuit diagram to connect one of the microbits to the ultrasonic sensor, and the blocks code to run the sensor and communicate the alert between the microbits.
I hope you enjoy this project.