Title text:
It's important for devices to have internet connectivity so the manufacturer can patch remote exploits.
Transcript:
[A store salesman, Hairy, is showing Cueball a dehumidifier, with a "SALE" label on it. Several other unidentified devices, possibly other dehumidifier models, are shown in the store as well.]
Salesman: This dehumidifier model features built-in WiFi for remote updates.
Cueball: Great! That will be really useful if they discover a new kind of water.
Source: https://xkcd.com/3109/
It sounds to me like your problem is human error, not the lack of a smarter machine. You can't engineer your way around people being morons. The greatest engineering minds have figured that out years ago.
So you think the reason a hygrometer can't detect humidity ten minutes before it exists in order to start cooling the dehumidifier's compressor to the temperature it needs to be to start working is human error?
No I'm saying you told your family to stop turning off the dehumidifier and they haven't stopped doing that. No amount of home automation or smart devices is going to change your family turning the dehumidifier off. You don't have a dumb system problem, you have a dumb people problem. And unfortunately a dumb people problem doesn't get solved by a smarter system.
Dehumidifiers are already automatic. Black mold isn't going to take over your bathroom in 10 minutes.
Turning the dehumidifier on ten minutes early means there aren't ten to twenty minutes where the shower's running with no dehumidification where condensation is able to settle on all the walls unimpeded, and the extra condensation takes a couple of extra hours to dry out again. Regardless of whether my family try to turn off the dehumidifier prematurely (and I only mentioned that as why I'd originally set a hygrometer up to graph the humidity in the bathroom, not as an ongoing problem), if that happens several times a day when someone showers, that's more than enough dampness for black mold to form.