Good comments Amberwolf ... I hadn't thought about "bigger" = size/surface area. I agree, to me a signal (alert/stop/turn) does indeed look better when it's a bit larger vs. just brighter/more dazzling.
For the most recent decade-and-a-half of my lighting quest, you can look thru my build threads from DayGlo Avenger that I'd already being doing when I came here, thru CrazyBike2 to Fusin Test / review bike, to Delta Tripper, to SB Cruiser (the present in-use build, which itself has a 10-year journey of experimentation), and the Cloudwalker Cargo Bike that just has pics of the lights it was going to use (never built it due to...stuff; not sure I ever will now).
That said I'm really curious about the rear light that E-HP uses and linked to with it's automatically increased brightness when you slow or come to a stop.
There are a number of that type out there.
The cheap ones usually use a ball switch, which is most commonly a cylinder with a long wire inside and a ball (bearing, etc) and a contact at one end. The cylinder is mounted on the PCB such that for the intended device orientation, it is either on (ball touching both wires) until the device is moved in a particular way, or off (ball away from the second wire) until the device is moved in a particular way. Some of the cheapest of these just bypass a diode or a resistor to cause the taillight to brighten. Some just turn on a few more LEDs (connecting them to power or ground in addition to the always-on ones). The better ones change the bias of a driver transistor or chip that's controlling the LED current for all the LEDs, by switching in or out a second resistor for that bias. All of these can be triggered by bumps and vibrations on the road, depending on the design of the ball switch and it's orientation.
But you could pretty easily add this type of switch to your own lights to have them autoactivate.
The more complex and expensive ones may use a MEMS device (accelerometer or similar) to detect the change in speed and trigger the sensor. These can be engineered to ignore bumps and other velocity changes that are not directly along the line of travel, either thru mechanical means within the MEMS, or via software in the light's MCU or the MEMS itself.
There are probalby other ways to do this, too.
Both methods can also be used to activate turn signals.
Hopefully JellyBean is enjoying the play time. Around here my greyhound Crumpet is looking for more indoor playtime, right now it's getting too cold outside for much more than quick walks.
JellyBeanThePerfectlyNormalSchmoo is a St Bernard, so cold outside is PERFECT for her.
Unfortunately that lasts about a month or two around here, most years. Even now we're having a "warm snap" that is warmer than she likes, since it's over 70F for the day's high.
Her idea of playtime is squeaking one of her pickles or canes (that have soda-can sized squeakers in them, so she can actually find and squeak it before she gets bored), while standing a dozen feet from me and refusing to bring to to me so I can throw it for her. Then she gets bored, drops it, and punches her nose into it twice and walks away, or sometimes comes over without it and slams her head into the side of my leg so I can give her head-squishes.
Sometimes she will actually bring it to me and I can then throw it for her so she'll race off to go get it, squeaking it crazily all the way back.... She might bring it back 3 or 4 times before she gets bored...drops it...and punches her nose into it to tell it to stay there before she walks off somewhere.
