Light Theremin
You have seen the light! This handy gadget will generate a 5v DC offset when you shine a bright light on it - very cool and useful for all manner of CV duties, such as sweeping a filter with nothing but a nearby light source, for instance. Naturally, the device also responds to being occluded or the light being dim or further away, by generating a lower output. Handy for your next performance in the dark!
The device comes with a handy kill-switch for when you no longer wish to see the light.
Available in two configurations: switch on the right, or on the left. Useful if you're making a handheld device that requires two - one for each thumb!