I attended AT&T Mobile App Hackathon in Plano last weekend. I made an iPhone app in less than 24 hours! It's a app that display lyrics while playing a song, it highlight the sentence that's being played, kind of like Karaoke. It's more of a proof of concept prototype. But I will continue working on it and will submit it to App Store. I will also make an Android version.
Here's video demo: (Sorry for the poor video quality. In shooting of this video, the camera went out-of-focus, I tried to manually adjust but that made it worse.)