The boyscouts pretty much nailed it when they coined the motto "Be Prepared to DJ." And Swedish headphone manufacturer Urbanears wants to make that possible with Slussen, an audio jack splitter and app combo.
The setup includes a narrow-profile splitter for simultaneously connecting headphones and a sound system to your iOS device, plus an app for the actual beat dropping. Urbanears seems to have its heart set on people specifically using Slussen at after-parties, you know because it's "the most powerful after-party weapon known to man" and all. But you could easily use it in your car or with a portable speaker.
The splitter costs $15 (though the red one is $20 for some reason), comes in four colors and can hang on a keychain. Meanwhile, the Slussen app has standard effects like BPM control, equalizer, scratching and crossfade, plus it allows pre-listening. And best of all it's free so you can use the app with any splitter you already own. [Urbanears via Werd]