Want to be notified when a web page changes? For example, want to know the exact second the Apple TV goes from “coming soon” to “actually on sale”?

Check4change is a Firefox extension, though it doesn’t require you to make Firefox your default browser. Install the extension, visit a web page, select the text you want to monitor and select a reload interval, then stop thinking about it.

For example, if you had gone to the Apple TV store page and marked the “coming soon” text, check4change would have notified you the second that text changed and the Apple TV went on sale.

Very useful! [H/T Dan Cormack]