Can help fill in some of the blanks for you. The toothbrush has bluetooth. Its bluetooth advertisement contains information about its operating state (running, idle, etc.), mode (brush, daily clean, etc.), pressure and some other things. The ESP32 chip scans bluetooth, detectes these advertisements, parses them and extras the data. It then sends it over to home-assistant.io which can use the data to trigger actions on any other connected device.

Right, he didn’t modify the toothbrush to do anything. Just picked up the BLE message going out and used that to trigger his lights which itself is just sending out a different BLE message as I understood it.

Your comment rewritten for our modern world: “Life Hack: My espresso machine automatically wirelessly controls third party accessories like my coffee grinder”

Can this really be true? Can you explain more about what exactly is going on? Your grinder must be controlled via a microcontroller (and your espresso machine must make the FCC cry?)? My grinder is a simple physical on/off switch that’s directly wired to the motor.

I have some capacitive (?) touch-sensitive lamps and a big switch for a ceiling fan. Sometimes when I flick the switch the lamps turn on

Used https://m5stack.com/products/stick-c myself

As someone who's done lots of automation and lived with a spouse that isn't as enthusiastic about it, one of the key things to think about is intuitiveness.

The setup of "automatically adjusts lighting based on finishing brushing teeth before bed" could easily be "the bedroom lights do random and frustrating things when I'm trying to get ready for bed". The problem is complex interactions are hard to see, like what happens when someone does something out of order, or adjusts the lights to their liking before brushing teeth, or is brushing early after a late dinner or garlicky snack but not going to bed yet.

That said, if you can do it without annoying others, go nuts! It's super fun, and it's a great learning experience to spend weeks interacting with your software from the real (physical) world. You'll find tons of edge cases, and figure out how to deal with race conditions, less than 100% reliable signals, etc.

Some of my most useful automations are very subtle, like turning on a couple inside lights as it's starting to get dark outside but only if there aren't any lights already turned on. If we're home (and have manually adjusted lights), nothing happens. Yet we never come home to a dark house (There's a similar automation for front outside lights too). This is quite a bit more complicated than a simple timer, yet is so intuitive that you don't even realize you're interacting with it.

Of course it doesn't. They've saturated the market though, so it gives them something to sell to people who already have a power toothbrush.

I bought one out of curiosity as to what it might add.

It’s sort of like a management consultant: The bluetooth allows my phone to tell me when I’m brushing my teeth. So I paid big bucks to find out something I already know.