Cuppa is a spiffy tea timer program for Mac (if only for its sound effects ;), itself inspired by The Tea Cooker from Linux. However, there’s an easy way to create a de facto tea timer, or run any kind of countdown, via the Terminal.
The sleep command allows you to run other commands or programs with a delay. So, for example, you could enter,
sleep 20; ps
which will pause for 20 seconds, then run ps to show your active tasks.
To keep you from having to stare at the Terminal window waiting for your tea countdown to finish, we’ll make use of the say command, which taps into your Mac’s built-in Text-to-Speech ability. (See System Preferences > Speech.)
So, assuming you want your Earl Grey to steep for four minutes, you could use something like this:
sleep 240; say "Your Tea, Earl Grey, Hot, has completed brewing."
Or for your Green Tea:
sleep 60; say "Green Tea processing complete."
Enjoy!