Technology

There’s probably a generic, dedicated chipset or board that does just this available for OEM purchase that they just wire into whatever they’re building.

Yup. It's called an Espressif ESP8266, and it's spawned a bunch of variants including the more powerful ESP32. It's a little microcontroller on a circuit board with an antenna on the board, cost about $1-$2 in quantity, out of the box it speaks WiFi and most variants now have Bluetooth also. It's got enough intelligence on board to run a simple IoT gadget, and if you want more it'll act as the communication module for your larger system board. And since it's got all the RF approvals (FCC, CE, etc) already done, it means you can add RF communication to your product without expensive RF certification.
In fact, use an external low voltage power supply (which comes with its own certification), and pretty much the only regulatory testing you need to do is to prove it won't spontaneously catch fire.

Anyway there's over a dozen variants of ESP-family chips and boards with various capabilities. Here's an example. Or that same example mounted on a breakout development board. See the pinout here- this little module is a proverbial tub of Legos with TONS of capability to unlock.

Then throw in some cloud platforms like Tuya that will handle most of the cloudiness so all the developer needs to do is write an app and sell products.