I have two Digi WLED controllers a handful of project kits, myself.
The WLED boards drive some addressable LED strings in my living room and on my patio. They hardly count as “project” kits, but learning about interfacing TTL logic with the LED driver boards was a helpful experience. I learned a lot about the different GPIO uses and modes.
For the project kits I’ve built, I’ve been focused around presence and environment sensors. Using esphome I’ve successfully built PIR (AM312) + mmWave radar module (R60A) presence sensors, natural gas detectors for kitchen and basement utility areas, and a water leak sensor for the laundry area. I had goals of building a 5-in-1 presence sensor, but you can buy products for those now; its a solved problem.
I’ve been considering a design for a sump pit depth gauge because that sounds like useless information that I’d like to have for some reason.
I’ll probably get interested in energy management soon, and will look into current clamps and tracking usage at smart receptacles.