LumenMill is a Windows and MacOS application for watching video, and playing computer games while doing stationary cardio. If your heart rate drops, your screen and sound are obscured by old-school TV type static. If you heart rate goes too high, a red screen and annoying beep tell you to back off. This software is created by Steel Rhino Technologies Ltd., which is a one-man limited-liability company in the UK. That man (me) found it was easy to slack off while playing video games on his recumbent bike, so created LumenMill to keep himself honest.