Final Scratch is a toy for DJs made by the folks at n2it, who have been scooped up by Stanton Magnetics. Final Scratch was in development for years, since around 1998.
The product is perhaps the most innovative way to play digital audio in a nightclub or party context; it's certainly the most outlandish. Final Scratch consists of your computer, software, an interface box (called the ScratchAmp), and two special discs. These discs have positional information on them. You place the discs on your wheels of steel, and play them back with your regular turntables, which are hooked into the ScratchAmp, which goes to your computer's USB jack. If you're playing a special Final Scratch disc, your computer will play back a selected audio file, with the speed adjusted by your turntable's pitch control. Nifty.
"Your computer" mentioned above should be a 500MHz Pentium-ish PC running BeOS. Yes, that's right. BeOS, the dead one. Final Scratch was supposed to be one of BeOS's killer apps. Unfortunately, it took too long and ended up killing off BeOS instead of its competition. Oops, it runs on Linux now, which comes with the package.
n2it sent Richie Hawtin and John Acquaviva some demo units for testing. They used the units (the original configuration, which included the disks, an interface box, and a new laptop) for around a year on the road, during the tour in support of DE9: Closer to the Edit. This works well for them, as they each have record collections on the order of 40,000 albums. Also on the promotional payroll are Kevin Saunderson and Surgeon.
The original release of Final Scratch was in June of 2002. It installed under Windows but was, in fact, running a customized distribution of Linux. Later versions have replaced this with a special version of the Traktor software from Native Instruments, which also runs on Mac OS X. Stanton also sells needles specifically for use with Final Scratch discs.