It's a sensor that goes inside the dryer, so it wouldn't be able to turn it off for you unless also connected to a smart plug, but this is also problematic as another comment pointed out. Many are stuck with typical dryers that are nothing more than a heat setting and a timer. If your machine already does this for you, then the product obviously isn't for you.

Or they could just have it connect wirelessly to a smart plug adapter instead of the internet/network

Indeed, sensing the moisture in the load is literally a decades-old feature; look at the dates of these patents, for example:

https://patents.google.com/patent/US3402478A/en

https://patents.google.com/patent/US3758959A/en

The ~199x dryer I have shares service parts with a dryer from 1965 and they are still available.

Sharing service parts suggests they aren't exactly the same, ie it has changed as times have changed. Also sharing service parts doesn't preclude them adding a moisture sensor and shut off.

Apparently you buy it because you 1) can't hear the humidity sensor alarm built into the dryer already that already turns off the dryer, and/or 2) are a useless gadget cuck who can't go without having it on your smart phone.

This is presumably for people that don't have such a choice. I'd have a decent dryer if I didn't rent, but I do and such things are typically included, and consequently are the cheapest money can buy.

To do this I'd need to integrate the dryer sensor with a smart plug.

The cheapest dryers (electric and gas) Home Depot carries around here have moisture sensors:

https://www.homedepot.com/p/Hotpoint-6-2-cu-ft-White-Electri...

https://www.homedepot.com/p/GE-7-2-cu-ft-White-Gas-Vented-Dr...

I thought they were required by law these days.

This assumes the units in my building aren't 15 years old ;)

Should have specified I'm not US :)

https://www.binglee.com.au/products/inalto-ivde45w-4-5kg-ven... This is a functional equivalent of what I've had in multiple rental properties in Australia. It has "Hot", "Hotter", and an egg timer.

It’s hard to turn a dryer off with software. Most are gas and even for electrics, smart plugs usually don’t support 240V. So you’d need a different kind of arm or hand for each kind of dryer.

> smart plugs usually don’t support 240V

Maybe not in US. In AU, for example, they do. Also I'm surprised to hear that. I would have expected them to be universal and work anywhere between 110 and 240V.

In the US a 240v plug is a physically very different plug designed for running high wattage domestic appliances like a dryer, oven, or electric range. Most homes only have one of these installed in the location where that appliance is expected to be. They are typically rated at 30 amps and are actually two phases of 120v. It is certainly possible to make a smart outlet that can handle two phases and 30A, but it would be expensive, and have limited market.

A smart plug must extract a small amount of power from the line to run itself--and that means a power supply that very well might care. There's little reason to make the power supply universal as the plug is part of the unit and the plug specifies the voltage. You very much do not want plugs meant for different voltages to be interoperable! (20+ years ago I had multiple run-ins with this. China uses 240V and one of the two plug types is the same as US 120V. My FIL would try to plug US stuff in without using the transformer and of course it would promptly self-destruct. By now most things one might be traveling with are universal voltage but back then few were.)

Not only are US 120V plugs different than 240V plugs, but the 120V/20A plugs are a superset of standard 120V/15A plugs--a 15A plug will fit a 20A receptacle but not the other way around. I do not believe code permits plugs for devices beyond this range--the really heavy stuff is always hardwired. I believe this is to prevent morons from trying to power their house from a generator with a suicide plug--forcing people to use a proper transfer switch that can't backfeed. I suspect this will change in the future due to how dirty small ICE engines are--as it stands things like electric mowers aren't very good because they can't get enough power to be good. Likewise, pressure washers--the high power versions are always ICE. Where I grew up you needed at least 4hp in a lawn mower--and you can't draw 4hp from a normal wall plug.

In the US the 240v outlet is a physically different shape and size, and there's usually only a few in each home, where powerful appliances are expected to be fitted.

You could probably fit an adapter, but I imagine smart plugs in the US are built with the assumption they will never have to handle such a high load.

Most are gas? Where? Every dryer I’ve ever used has been electric, both homes in the US and rentals abroad.

And as noted in another comment, even the cheapest dryers in the US have sensors (and have for decades).

This is a very US centric view. In the countries I have been I only encountered electric dryers. Personally I have a heap pump dryers that does a good job at turning off.

For what it's worth, I've lived in the US since the 70s and I don't think I've ever encountered a gas dryer. Could be regional, though.

Utility natural gas does tend to be regional. Where it's available, it's most often much less expensive to use natural gas for heating than electric resistance heating, although you usually have to pay more for the appliances. If electricity is inexpensive, gas is less desirable. Most gas appliances can be adapted to use propane, and propane deliveries are available in a wider area, but you probably want several propane appliances to justify the plumbing and the storage tank.

Electric heat pumps can be more cost effective than gas though, but there's details.

Utility natural gas is obviously pretty widespread across Canada. I've never seen nor heard of a single person with a gas dryer.

Based on my (obviously limited) set of data, I'd certainly argue against "most" dryers being gas-powered.

Most dryers are gas? Where do you live?

I've never owned/used a dryer that was anything other than set a timer and turn it on.