Back in the pre-iPhone days, a little gadget called the Pacemaker Pocket DJ made a big impression — it was the world's first portable DJ system. But one look at the App Store let us know that it's days would be short lived. And they were. But now the original team is back with a new app called, simply, Pacemaker. This free app — add-on effects are available for in-app purchase — lets you mix, loop, blend, and drop all you want, using tracks from your own music library or any of the millions of tracks on Spotify.