See also the "McLaren Snorkel"[1] in Formula 1. Not actually cheating, but it was also a brilliant piee of engineering, and it was banned pretty quickly.
TLDR: in F1 you're not allowed to have a variable rear spoiler (i.e. high downforce in corners but low drag on straights). But the rules only specified hydraulic or mechanical devices were banned. McLaren engineers came up with the idea to stall the rear spoiler on the straights using a flexible tube which led air from the front spoiler to the rear. The driver would use his knee inside the cockpit to block or open the flow in the hose, so no mechanical or hydraulic mechanism was used.
And this is my primary problem with Formula 1. Any time anyone actually innovates, it's banned in short order. The whole thing is about dealing with the arbitrary restrictions imposed rather than about making the best possible vehicle.
TLDR: in F1 you're not allowed to have a variable rear spoiler (i.e. high downforce in corners but low drag on straights). But the rules only specified hydraulic or mechanical devices were banned. McLaren engineers came up with the idea to stall the rear spoiler on the straights using a flexible tube which led air from the front spoiler to the rear. The driver would use his knee inside the cockpit to block or open the flow in the hose, so no mechanical or hydraulic mechanism was used.
[1] https://scarbsf1.wordpress.com/2010/03/11/235/