A guy I know tried to build a business around a physical pomodoro timer a while back - https://www.indiegogo.com/projects/timechi-your-smart-produc...
A useful addition for those using this in an office, and even for those who don't want to look at the screen for the remaining time, would be to have an LED (maybe as a nice lightbar) on the top of the device which shines red or green to suggest to those who can't see the screen (viewing from the other side) if you are available to be interrupted or not. You could even make it as a progressive light bar if you were so inclined.