As part of my ongoing kickstarter addiction I’ve recently acquired a MaKey MaKey – a sort of universal keyboard adapter gadget based on an Arduino-type microcontroller, that lets you turn virtually anything that conducts electricity into a USB keyboard or mouse.

The board comes supplied with a pack of crocodile clips and a nice long USB cable – on the MaKey MaKey website there’s a list of ideas to try (apparently bananas work well as a piano). All you have to do is find something suitably conductive, connect them up with the clips, and away you go.
The simplest interaction is creating a space bar input – this Olympic hurdle game from the ONE Campaign works well as something to try.
I’ve done a bit of experimenting to see what conducts with the aim of making controller doodles in my moleskine notebook. Conductive paint from these guys works – interestingly metalic effect paint and ink doesn’t work (I suspect as the metal is in a suspension).
The easiest and most sketchable I’ve found is using a big chunky graphite pencil like this one KOH-I-NOOR Jumbo Woodless Graphite Pencil 6B available from amazon for a couple of quid:

You have to press quite hard with the pencil to get a good circuit – shorting the gap between the U and the M with your finger is enough to register as a space bar press:

So there you are – a sketchable, moleskine portable control interface! (even if it does get a bit smudgy after extended play).
Check out the ONE Campaign race against hunger game here.