I have one of these in my car, and it's been great! Got it as I was starting to get a check engine light intermittently, and it reported the exact code, which lead me to what to fix, and clear the code before I could get the time to do so. The big bonus is that for the lifetime of the device, if you get into an accident that disables the car, it will call not just emergency services, but three people you designate (note: I haven't tested this. Don't really want to.).