LED strip light controller. The cheap ones have none or limited integration with most HA platforms and I can't justify spending on the more expensive ones just to add Homekit.

AQ monitor. I work indoors a lot and I think the migraines I've been getting might be caused by dust, VOCs, or pollutants. So will be good to back that with some data.

Robots. Lots and lots of robots. Some roll. Some walk. None of them do anything useful. :-)