DJing on the iPad is becoming a bit of a thing, it seems. A device that you wouldn't think would be ideal for such a high-pressure job seems to have been adopted quite widely, be it as storage that fits into some DJ decks, or as a standalone DJ mixing system.ION has launched a set of stick-on, capacitive touchscreen controllers at CES that aim to give you DJ-style controls, in physical form, on your iPad. You might argue that's pointless, given Apple's quest to murder the physical button, but the demo at CES was kind of cool, and it might prove somewhat useful.Simply, the system is a series of plastic attachments with suckers on. These are placed on the iPad's screen - it doesn't matter where - then capacitive attachments are placed on the underside which move, brushing the screen and giving you control of the ION app.On the software side, it uses IONs iDJ2GO, which is also available with a physical controller pad. This hooks up to your iPad via a cable. The software is pretty much what you'd expect. There are a couple of decks, a crossfader and the usual controls for tweaking sound.\u00a0A simple enough idea, and one we've not seen from anyone else. It's likely to be a low-cost way of using your iPad to DJ, and we found the demo pretty impressive in the scant few minutes we spent with it at CES.