A speech therapist wanted to implement the idea. The need to have the microbit 'hot pluggable' arose. This means that the system needs to cope with the microbit not being plugged in when it starts up as well as when the microbit to be plugged in. The software also needs to handle having the microbit unplugged and then plugged back in again.

I hadn't thought of this when I first built the system.

Ooops.

It took me a while, but I figured it out and now the updated code is posted on GitHub.