MyTunes has been on the App Store for a little while. It's developed by SRS that uses that company's patented sound enhancement algorithms to make music sound "better." It's not completely clear what the algorithm does (as SRS wants to keep it secret), but basically, the tech boosts and lowers certain qualities in audio to make it clearer and more listenable.
MyTunes Pro is the new version of MyTunes. I saw it in action at CES earlier this year, and it's now available for the iPhone and the iPad (here's the HD version). The biggest update is that you can use AirPlay directly with the app. This lets you push your iTunes library through MyTunes Pro's enhancer, and then kick it out to an AirPlay system.
You'll also find new controls for a system called "TruSpeed," which will speed up or slow down your audio without changing the pitch (so you can listen to more podcasts in less time). A new "workout mode" lets you gather songs by tempo (BPS). The interface of the app has been updated as well. Unfortunately, it's still pretty laggy (and doesn't really feel like a native interface), but it is a little easier to navigate and use than earlier versions.
MyTunes Pro is free to try, so if you just want to hear what it does to your music, you can download it and give it a try (you get 10 minutes a day, unless you pay an in-app purchase of US$6.99).
It's an app that's of somewhat limited use, because you can only listen to music in your iTunes library. iOS doesn't let audio from services like Pandora or Slacker get processed. Still, if you listen to music coming off of your iOS device all day, and would like it to sound even better (or just want to have a really capable EQ to use on it), MyTunes Pro should do exactly that.