Alright, this is pretty cool. Pyro is a crazy music app that seamlessly mixes your tunes like a DJ so you never miss a beat or have an awkward pause between tracks. It works with Spotify Premium or iTunes, where it will run some crazy math to smoothly transition from song to song.
Here's a great video which breaks everything down the app in-depth and gives you a earful of examples. It's pretty wild.
Available for free in the App Store now, it's a no-brainer download. Get after it.