One of the ways that Microsoft's Surface has always distinguished itself from more mundane touchscreens is in its ability to recognise physical controls placed; now the iPhone can have something similar. dsLabs have put together a DIY hardware knob that can be used with a virtual control on the iPhone (or, indeed, another multitouch-capable touchscreen device), using little more than some conductive tape.
Video demo after the cut
Basically, the knob fools the display into thinking that there are two points of finger contact touching the screen; that way you can rotate the UI by twisting the physical control. If you haven't any conductive tape, dsLabs suggest using a small enough knob that your fingers can brush the iPhone's touchscreen, though that seems a little like cheating to us.
Of course, the physical control isn't actually being recognized by the iPhone in any meaningful sense, but it would make for a more tactile way of controlling something like Korg's brilliant iElectribe app for the iPad. Demo in the video below.