As a designer who also enjoys critiquing sites, I would gladly try this out (as a tester and customer) - if it weren't for you requiring feedback to be in video/audio form. There are just so many problems with this.

Namely:

* Video recording is cool. But I'd much rather have a hotzone graph of mouse activity than having to waste my time watching each video manually, with the option to review each video.

* Not all offices that might want to use this are SF startup environments. I could never get away with wearing earbuds/headphones in my office to listen to testers. And I work at an office smaller than many startups.

* I can't name one designer I know that would have the patience to listen to 50 minutes of people talking about their website, no matter how constructive it is. * Your average tester will not speak very good English. If I'm purchasing your service I would be pissed if I couldn't understand what they are saying.

* Most people express themselves much more clearly and concisely in text. Since most (if not all) of the people testing will be from generations that grew up with IM and texting, I am sure this will lead to a much, much higher average review score.

I'm ranting a bit here, but basically TL;DR - Text reviews by testers is simply a better option for your business.