This guy, with the help of some peers, designed a new type of brake light a few years ago. It's engineered so that it not only lights up when the driver touches the vehicle's brakes, but it also lights up more or less of the light strip when the driver presses lighter or harder on the brake pedal. Current standard brake lights only have two states: on or off.
That means that drivers around you could see when you're just tapping your brakes gently, and they could also see when you've slammed them on. Hopefully, it would allow other drivers to respond more appropriately to your vehicles movements by giving them more information about what to expect.
Would you want this on your car?
Here's some additional commentary from the engineer on Reddit:
"In doing my research for a reactive brake light I had come upon an Aston Martin (I believe) from the 70's which had brake lights that got brighter as the brake was applied. Unfortunately, as with the BMW design, I don't think this is very good design."
"BLIP on the other hand, is a constant brightness when applied and works in a gradient array. It's easy to see the maximum values so there is little guessing involved in how hard a person is indeed braking."
"Legality, though, is a whole 'nother problem."