The Power Magic EZ requires the vehicle to have an OBD port with CAN bus connectivity.
All the cars manufactured after 2008 have in-built CAN bus connectivity.
If you own a car manufactured before 2008, you can find out if it's equipped with a CAN bus connection in the OBD connector from here.
You can also check the availability of CAN in your car here.
CAN (controller area network) is like the nervous system of the car. It is a way to transfer data between all interconnected devices in a car using as little wiring as possible. There are other bus systems but CAN is the most widely used one.CAN uses pins no. 6 and 14 of the OBD connector.
CAN may be used in a car and not be connected to the OBD port (at least for pre-2008 vehicles sold in the US).
OBD is just an interface to plug a diagnostic tool. It was created as a standard way to allow repair shops to primarily monitor vehicle emissions. Knowing that, it makes sense that Tesla Model 3 (being an electric vehicle) has no OBD port. And the only reason the Model S and X had an OBD port was probably because of the law, and Tesla applied to not be required to include the OBD port in the Model 3.