Ok so it won't win any awards but not many startups can have a prototype done in 5 minutes!
What you're suggesting at the core is basically what mobile transcoders already try to do, and any document classification system which needs to work out the most important content. It's a hard problem but there is plenty of thoughts out there to build on.
What you could do, even, is build a "meta-service" on top of something like Google's transcoder, where you pass the site into Google, then transcode /it's/ results to add a nicer style and the usability stuff like the feedback link. That would be a way to get something started pretty quickly, and you could use the feedback to see where Google isn't good enough, and therefore how to improve the service.
Displays content in a smaller, harder to read font than my default.
No button to give feedback "you messed up, I can't read your 'readable' version".