[ErikAugust]

Had this idea - except mine would be a variation for training.

Instead of too fast, it would make an insane buzzing sound if too slow. The problem I would think is accuracy. You hit a bad area, suddenly you are being annoyed even though you are on target.

[stereo]

I've configured my cycling GPS to auto-pause when I'm going at less than 5 km/h. So sometimes, while I'm struggling to pedal up a big hill, my GPS adds insult to injury and auto-pauses with a sad beep.