Has anyone made this app? What should I search for?

Here’s what I need: A program that I can set up a time frame, and each day during that time frame, if I am doing something on the computer, it pops up with a message.

So, if I am still playing on the computer at 10PM, it would tell me to go get ready for bed, but if I’ve already left the computer it won’t do anything. I have an alarm program that will pop up a message at a given time, but it doesn’t recognize when I am not active on the system (and if I don’t clear the message, that interferes with the next alarm).

My MS Outlook calendar seems to work for that.

Google Notifier will work too, in that it can give you an event alarm that goes away in short order whether you’re sitting at the computer or not.