[patio11]

Three Rings (the guys behind Puzzle Pirates) have something, too.

My favorite feature was hooking it up to loudspeakers and playing a particular sound from their game every time the business made money, with the sound corresponding to how much money they made.

They eventually disabled it, because the constant interruptions were starting to annoy people. This is a nice problem to have.

[prawn]

I remember reading years ago that Amazon had a similar feature in their warehouse in their early days. They also had to turn it off once it became a constant ringing bell!

[trafficlight]

It's still nice feedback to have in the beginning. Makes it feel like you are actually accomplishing something.