I already implemented distance calculation on my dev repo. Only in km for now.
You can chose what to display in each line, steps or distance.
The widget takes too much memory now, it is not even possible to go to the settings app without running into memory problems. I will need someone to assist me with this.
I am going to open an issue now for that.
Edit: there it is https://github.com/espruino/BangleApps/issues/296
Suggestion: show kilometers instead on steps with that bigger (green/white) font. Make step size configurable.