do you have a HomePod or appleTV? (these are known as homekit home hubs)
is at least one of them the newer versions with thread?
What sort of "heated clothes dryer"?
where are you? Product availability varies by country. the different power distribution systems also affect what will work.
any homekit automation will require a home hub to run, there has to be some sort of smart device to actually run the automation. So you will absolutely need one of these.
and if you have the thread version, it opens up your options for sensors, as well as potential options to control the dryer.
Clothes dryers are typically high wattage, which will limit what you can use if you're just looking for a smart plug that will simply switch the power on/off to control the dryer.
If the clothes dryer has more than a simple on/off switch (and maybe a humidity knob), it may or may not work well with just turning it's power on or off.
You may be able to kill 2 birds with one stone, HomePod minis have humidity sensors built in, so you could just put one of those in the cupboard, you would then just need some way to control the dryer.
If you do have a home hub with thread already, the "eve home" sensor will monitor humidity, it's around $100.
Most sensors may not be rated for the heat of the heated dryer, the one from eve is rated up to 122F/50C. so that's another thing to take into consideration.
eve also makes smart plugs, but they vary in wattage from 1800 to 2900 watts depending on what kind of power grid you're connected to.
once you're got those working, making an automation is fairly painless. The only thing to watch out for is automations will only trigger when "humidity falls below 40%" (you can pick any number). Meaning if you turn the dryer on and it's 38% and it drops to 28%, the automation will never trigger, since the humidity was below 40% the entire time, and never "fell below"