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Chicago Parking is the one I really know, but it hasn't been updated in over a year, so I have stopped using it. The same developer had similar apps for LA, NYC, etc., but I'm not sure if those have also been abandoned. I think you pretty much have to be in a large urban environment to get good information. I have seen Parker on the app store, but I have never tried it out for myself It has quite a few positive reviews on itunes.