I had a blast playing with Xamarin Forms and SVGs which end up with the following which works on iOS, Android and Windows UWP, checkout the videos for Android and iOS apps:
Credit for original design idea goes to Mikael Ainalem:
The SVG is created dynamically, based on the position of the text-boxes and the button, so it will work on any number of text-boxes and buttons. The actual SVG for the login screen in the videos, looks like this:
