Really just wanted to learn how to use the hammer, in this case. But still, yeah... you're not wrong ;)
I've seen some people using a fan that they modulate with a PID to control the temp, which is on my list of "someday maybe" projects, heh. I wanna say there's even an existing product that does this, but I forget the name.
Fairly easy to glue together sensors to roll your own, I made an egg incubator with basically the same pieces that had a webcam too, http://www.velvetcache.org/2018/03/04/chicken-cam-incubator-...
I like the reuse of the phone though, I wonder if there is some sort of bluetooth board out there that can bridge the phone to the gpio stuff.