Enable GPS Prompt - has no effect.

Also, it would be wonderful to have a dedicated page explaining each Extra feature.

Add option to Zoom that hides + and - buttons. Most users are familiar with using Gestures to zoom, and now they have to wait for zoom buttons to disappear - as these buttons cover part of website on smaller screens.

I would suggest adding a note on screen - that if people want to use HTML5 geolocation, they need to use SSL (HTTPS). In other words http://yoursite.com will not return position, but https://yoursite.com will.

Quote from Google regarding WebView:
For applications targeting Android N and later releases (API level > M) the geolocation api is only supported on secure origins such as https. For such applications requests to geolocation api on non-secure origins are automatically denied without invoking the corresponding onGeolocationPermissionsShowPrompt(String, GeolocationPermissions.Callback) method.