One of the bigger pieces of our last prototype was the board we used to
charge the lithium battery. The actual components necessary can be tiny,
but to make it more flexible and easier to use there was a lot of extra
stuff and dead space on adafruit board. This one is also from adafruit in a
much smaller form factor. I don’t think the male Usb-a plug will work for
us, but there are similar boards with USB mini jacks that would.
That would bring down the minimum size without needing a custom board and
circuitry - which I’m keen to do while we are still early stage hardware
prototyping. I’ll shop around and try some options.
To really downsize we are going to need a smaller battery and power
management strategy. We are going to get some data on sleep/wake-up and
reconnection times to see if we can sleep some of the device some of the
time and keep the perception of being always connected.