Contrast Checker

Been thinking recently about how design tools can be more representative of how the web works, and help designers to make better decisions around accessibility.

I love Stark by @Cat Noone, @Michael Fouquet and @Benedikt Lehnert, but it would be awesome if that functionality could be made even more seamless, and respond automatically to whatever background is behind the text. A bit like spellcheck in word processors. This is just a concept for how that might work, made in Principle. I got lazy and used the results screen from Stark.

Has anyone seen anything like this before? Any other ideas for improving it?