I found out yesterday what it was, and yes, its a little black box about the size of a cigarete packet that you have to buy as an extra and plug in. Cost about 100 euros (in Germany)on top of the cost of the unit.
I ended up buying an AEG unit. They do mainly household appliances and are reasonable quality. Hope thats the same for car hifi.
It has Bluetooth incorporated, 4x40watts RMS and a woofer output. It also has a remote control that straps onto the steering wheel, but I don't think this will ever get used.
Thanks for the replies.
