Understory

A body-worn environmental puck the size of a large coin. It logs air quality, noise, and UV for a working day, then syncs when you get back. It clips to a collar or a strap and disappears; the only control is a single recessed button.

The enclosure is ultrasonically welded, no seam a thumbnail can catch, rated for a walk in the rain but not a swim. A year of runtime from a cell you can replace with a coin.