I found this fascinating:
Sabbath law prohibits Jews from performing actions that cause a direct reaction; that would qualify as forbidden work. But indirect reactions are, well, kosher. In Hebrew, this concept is called the gramma. There are two types of grammas, Ottensoser tells me. Say you hit a light switch, but it doesn't come on immediately - that's a time delay, a time gramma. There's also a gramma of mechanical indirectness, like a Rube Goldberg contraption in which a mouse turns a wheel that swings a hammer that turns a key that launches a rocket. You can't claim the mouse actually launches the rocket.
Ottensoser gets manufacturers to build the easier time gramma into their products. Rabbis differ on how much of a delay is required; the Star-K rabbinical authority, Moshe Heinemann, authorizes a 5-second lag. To be on the safe side, Ottensoser increased the delay to 15 seconds and a random wait of as much as 10 seconds. Why? "An indirect action is one where you can't predict what's going to happen," he says.