I can’t believe I haven’t come across the Instructables website before - it’s a kind of collaborative How To for all sorts of things. These Throwies are a great addition from the Graffiti Research Lab (good name), which is part of the generally excellent stuff going on over at Eyebeam OpenLab.
Throwies are basically an LED, a battery and a magnet all taped together so that you can throw them at ferromagnetic materials (you know, steel sculptures and cars…) and they stick. Very playful, very amusing, very clever. The only big downside is throwing away lithium batteries…
The Graffiti Research lab have a great clip of them in action and the Instructables site has, as you would imagine, instructions on how to make them.