This exists and is what Hound is built on. Rubocop runs lint checks against your Ruby code: https://github.com/bbatsov/rubocop/ . The Emacs integration is great; it highlights failures in place. Hound looks interesting, but having Emacs/Vim integration gives you a tighter feedback loop, so you don't have to wait until Pull Request time to discover these issues.
Check out the pomo gem. It works in a very similar way plus it adds a 25-minute timer for pomodoros. If you add your .pomo file to git would do the same integration.
I also recommend checking out Audiogalaxy. It works surprisingly well on 3G and is a great way to access your entire music/podcast collection from your phone. I use it all the time.
It's funny, the same thing happened to anywhere.fm, of which lala is basically an updated version. They made a fun way to listen to all of your own music online, they got bought out, and they disappeared. Maybe YC should fund another anywhere.fm?