Been thinking about a game you can progress through by walking irl, but not sure if C3 can tap into a phone's step counter? It looks like C2 wasn't able to do this, but I can't find any search results for C3 on this topic.
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That would probably be a feature request as it looks like steps is a newer feature for the phones code. However you can still make your own with the acceleration and orientation, or possibly using scripting.
You can try using a Cordova plugin that gives access to the android/ios health app data which usually includes the step counter. That requires JavaScript usage and your own Cordova setup, however. The only plugin I could find is this one: github.com/dariosalvi78/cordova-plugin-health