It turns out that humans are very bad at noting the absence of a signal. Computers, on the other hand, are perfectly happy to use an expired timer to generate

It turns out that humans are very bad at noting the absence of a signal. Computers, on the other hand, are perfectly happy to use an expired timer to generate mail, a dashboard icon, or any other shout for attention that you please -- as long as you actually set it up. Paying attention to it is still a human problem.