The extension works with any multi-touch screen, not just mobiles. I like the idea of the extension, my only hesitancy in using it is that it sets a few scene variables. You haven't documented what the variables are, or what values they hold.
Generally, an extension will have a set of functions that get called to retrieve a particular value. In the case of this extension, at least 'getter' functions for things like angle from centre and distance from centre.
If you can modify your extension to do this, I think it'd be a great asset tot he GDevelop extension library.