I'd like to explore the idea of waiting with my sketch, by creating something that responds to the time of your interaction with it. I'm imagining an LED that is embedded in an object that you can pick up and hold, perhaps a paper mache ball or an ice globe. The LED lights when you pick up the globe, and turns off when you set it down, but it's not a simple on and off -- instead the LED fades depending on how long you held the globe: a slow fade if the globe was held for a long time, a short fade, if the globe was held briefly. I may play with animating the light in some way while it's on -- making it pulse or flicker or change color in some way. I may also try the reverse -- having it turn off when you pick up the globe, and slowly turn back on.
Feb 15, 2011: I've been testing the program, as well as the ice and parts. The circuits aren't seeming to work when encased in the ice (the water is shorting them), so I think I'll need to use heat shrink around the leads. The LED illuminates the ice in a really nice way, though.
Feb 18, 2011: Yesterday I got a couple of version of the program working. In one, the LED starts dim, becomes bright when you hold it, and fades out when you set it down. In the other, I tried a suggestion of Teroy's and flipped it so that the LED starts bright and gets dim when you hold it. I've just been prototyping it with a small paper globe, and I haven't incorporated the tilt sensor yet. I know that will change things... The tilt sensor is still a little finicky, so I think I need to play with the pull-up resistor value (perhaps?). This is the biggest challenge I'm facing at the moment.