We've launched independent registration: Informant is now available to all Ruby on Rails apps, not just Heroku – check out http://informantapp.com and get your app hooked up in no time!
The Informant reports invalid form submissions (e.g. too many characters entered, invalid characters used) and reports common mistakes. I like the direction and it gets me thinking of other ways they might automate and quantify usability issues.
The Informant
Product Hunt
The Informant