There is some redundancy, though Can-view will give you considerably more data, especially from the hybrid system. I have a ScanGauge now. I purchased it mainly because of the price (a used first-gen SG bought for $90) and no installation. If I had Can-view, I doubt that I would use a SG.
Your Nerd titer will go up considerably, and you don't "need" both as almost everything (if not everything) you can get on Scan Guage is also on CAN-view. But, it would be nice...I think if I were to get both I'd have the Scan-Guage set up to display the trip mpg data and the CAN-View on the car parameters that I watch (ICE RPM, Amperage, etc.) That said, you're going to have to make a special adapter to allow you to use both at the same time as there's only one OBDII port on the car. Hydrygas built one of his own at some point in the past, so it's doable, but it's not something that's easy or cheap to go out and buy.
Thanks for the input! The idea of boosting my nerd factor is rather appealing I mean, I think one would be hard-pressed to find a Prius owner that is not in constant pursuit of nerdiness!
