The disclosures in the patent aren't what they are suing you over. Read the claims. Patents like this often have a lot of stuff shoved into the disclosure so that they can keep the patent application alive to write more patents based on the original disclosure. The claims appear to be written to read on devices like yours: My knowledge of your system is a bit dated, but I thought you had a device that you plugged into a port in the car instead of a manufacturer-installed thing. This is why this patent has a 2007 priority date, but a 2018 application date: they essentially wrote a ridiculously broad disclosure, and kept filing patents based on it.
Dataspeed did appear to have tried to invalidate this patent in 2019 (see the IPR documents linked there), and succeeded on all but claim 20. If your device does not have a relay which shuts off its electrical connection within the car, you're probably safe. You could try to invalidate it, but you should read the docs from the IPR to see what Dataspeed did and what you might need to do.
My gut-check guess is that claim 20 is probably not going to get invalidated unless you can find some weird after-market car part from before 2007 which does a safety shut-off of a car component.