I, too, wrote a simple timer for my own use that I've posted for others
to use. Your program sounds much more capable than mine but maybe some
will find mine useful, too.

This is a single 'channel' timer that dings when the time is up. I find
it very useful when I'm baking, or watering the lawn, or waiting for a
tv program. It has large numerals so it can be read across the room.

Take a look at http://moya.us/Examples/