Just for reference, the official ToyotaPro Mongoose cable costs a whopping $482.63 !!!
You'll also need the GTS TIS Techstream software (Windows only), available directly from Toyota.
Once you've installed the software and the Mini VCi cable driver on your laptop, you can connect the cable to the OBD-II port (usually located under the steering wheel) and customize your vehicle to your liking.
As mentioned, you can customize the seat belt beeps, door locking options, head-light options and so on.
I bought one for myself and managed to change seat belt options on a 2016 Toyota Corolla.
I recommend using VCI OBDII driver v2.01 (requires 3 manual installations using Device Manager), after which the cable should be recognized by the Techstream software. Also note that the Techstream software requires a serial number to function. You can get one from this forum..ask a user who goes by the name Autokent.
Here's a good video on Youtube which goes through the customization process:
Now, if you're feeling at bit adventurous, you can try using a wireless OBD-II module, such as the one from Carista.
Carista has an app for both Apple iOS and Android phones which can connect to it and do pretty much the same as the Techstream Windows app. Here's a Youtube video showing Carista in action.