Experiment with Bluetooth by seeing how far you can make the message travel reliably.
As long as there are no obstacles, Bluetooth messages can travel quite far between devices. Work with a partner and see how far apart you can get while still sending messages to each other.
Investigate what types of material can block Bluetooth messages. Try to find ways to block the Bluetooth messages being sent.
Will it work in your pocket?
Will a cardboard box block the signal?
What happens if you wrap the micro:bit in aluminium foil?