I’d be interested to see a battery-less ring that uses the mechanical energy of the press to power a BLE transmitter to trigger voice input on a watch. I feel like it’s much safer, plus it has no fixed lifespan.

How will a single press provide that much energy?

Piezo

It's a single press, which has to power the microphone for several seconds, and wireless connection to communicate with the sync device, even later if it isn't immediately available. In what way would piezo generate that much energy?

> BLE transmitter to trigger voice input on a watch

I suggesting triggering input on a watch, not voice recording on the ring. In my suggestion the ring would be a ‘dumb’ input device.

I see. However that misses the point of always having the function at hand, 24/7/365. There will be the off time when you remove the watch to charge it for instance, or times when it may be inconvenient to wear a watch.

Your use case would be another product, likely with a different audience.

Mentioned elsewhere: this is why they didn't go with a rechargeable battery.

I suppose it would be possible to design the ring so that any pillowing would occur only in outwards expansion.