Which cars work with Speedometer on CarPlay?

Speedometer works with every car that supports Apple CarPlay. Apple maintains an official list of CarPlay-compatible vehicles at apple.com/ios/carplay/available-models — but in practice, almost every new car sold since 2018 supports it, plus aftermarket head units from Pioneer, Sony, Kenwood, Alpine, and others. If your car shows the CarPlay home screen when you connect your iPhone, Speedometer will appear there.