The app is called SongSwiper, it’s available for free in the App Store and it was updated yesterday to include Retina-ready graphics for the iPhone 4 and iPod touch 4th gen. SongSwiper is basically a controller for music playing from the standard Apple iPod app, but it allows you to control songs with swipes and taps instead of buttons, as in the iPod application.
The app looks a lot like Bowtie or Coversutra for OS X in the way it displays the artwork for a song currently playing. Unlike the aforementioned Mac apps, though, SongSwiper can’t live on top of your desktop – you’ll have to open the app every time if you want to enjoy its feature set. You can change between songs with a single swipe left or right, or adjust volume with a swipe up / down. To play and pause, double tap on the artwork. You can shuffle, manually pick songs from your Library.
SongSwiper might be the perfect app for those who use the iPhone in their car a lot and find it easier to swipe on the screen rather than having to point to a specific little button. The app’s free, so you should give it a try.