Pick up a CP9180. The CP9175 does give Freeze Frames but for another $30 or so, you can get the CP9180 which gives live data. While you may not always need the live data, it is good to have it. IIRC, the CP9180 was on sale for $150 or so this past week at Advance.
I have the CP9145 (older version of CP9180) and the CP9135 (older version of CP9175 but no freeze frames).