Algoriddim (DJay dev team) have decided to put their support behind the Griffin DJ Cable as detailed here on their website.
The cable appears to operate in the same way as the Stereomusik Systems splitter but is reported to be of better quality - although I can't verify this as I haven't got the Griffin cable (yet).
You can purchase the splitter directly from their US website here for $19.99, or alternatively HMV appear to be taking pre-orders for any UK customers at a price of £9.99 with free delivery.
This will still mean that you have a MONO PFL signal and a MONO Master signal - I'm sort of hoping that maybe iOS 5 might bring us some hope with dual Stereo capabilities? - wishful thinking of course!
Thanks to Palm Sounds who posted detail on this first!