Given that the user will typically have their watch on them as well, why not make the ring a battery-less BLE transmitter that triggers voice input on the watch? It’s still one-handed operation, but now the battery life is infinite since there’s no battery? The disposable ring seems like a solution in search of a problem to me, unfortunately.

Example button: https://core-electronics.com.au/self-powered-wireless-switch...

I imagine the reason is reliability, but USD$99 plus international shipping every two years isn’t worth that to me, sorry.

Aside: I loved my kickstarter pebble and my steel, btw!

Piezo switches like the one you linked have a minimum size to generate the power necessary, and that minimum size is larger than the entire current ring.