Found a magnet-activated, battery powered LED board+controller on AliExpress (https://a.aliexpress.com/_mNudMLl) and turned it into a (chunky) ring with a quick 3D print:
Mastodon is the best way to keep up with what's happening.
Follow anyone across the fediverse and see it all in chronological order. No algorithms, ads, or clickbait in sight.