And the real product pictures now:
Short demo of touch functionality (will post later on the bluetooth mesh network functionality):
Sorry for the solder bridge replacing the R20 inrush current limiting resistor..that's just temporary until I get the real component . And yes, the capacitor across the bulb is still needed but it's a very small one of 0.1uF/250Vac and it should fit near the light bulb on the ceiling (only one is needed if there are two light bulbs on the same circuit).
The aluminum foil wrapped around that sponge is to "extend" the capacitive sensor so that it reaches the front plate fake plastic button. The 3d printed clear plastic around it is to hold it in place and also to spread the small leds light.
Everything is custom made except for the front plastics.
Here's a courtesy heads-up.
I just now stumbled across a circuit:
that allegedly can operate on as little as 10na while collecting energy, which it then uses to power a small pager motor once a threshold voltage is reached.
It also has the virtue of utilizing inexpensive jelly bean parts and not relying on gigaohm resistors, which in the Dave Johnson circuit turned out to be so large that I lack the means to verify their specs through measurement after they are delivered.
This other guy instantiated the circuit as a PCB, and he made the gerber for it available as a free download: https://hackaday.io/project/159691-electron-bucket-extreme-power-management-module
If it turns out to be true that the circuit can both collect the current and trigger at a threshhold voltage all with just 10na of overhead, then on its face it sounds better than the David Johnson circuit turned out to be and possibly also better than many/most/(all?) of the commercial chips that we've reviewed on this thread if paired with an appropriate amorphous solar panel.
But wait! There's more. There appears to exist an equivalent single chip voltage detector that also consumes a mere 10na of current: https://www.akm.com/content/dam/documents/products/power-management/power-ic-for-energy-harvesting/ap4405aen/ap4405aen-en-datasheet.pdf
It's itty bitty, so it's probably a great fit for your uber-compact design.
"But I want more!" I can hear you say. "I want a total step-up solution! And I want one that doesn't use a transformer!" Well, of course you do. Who wouldn't? Apparently, a 0.2v transformerless step-up solution does exist as well. I'm just not sure where. They developed it for a customer who wanted to harvest energy from... bacteria. Actually, the official term is "microbial fuel cell." The chip is the AP4470, and thankfully it can also be powered by solar, without bacteria.
But can we buy it? Or is it just another inaccessible research project? I don't yet know. Can you read Japanese? The trail of bread crumbs written in English seems to run cold after the above link, but there's more about it that's written in Japanese. Argh.