The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Red Foundy:
Dude Where's My Car - Chicago stores your cars license plate number and allows you to store your current parking location to help find your car faster. In addition DWMC helps you to quickly search the City of Chicago Open Data Portal Towed Car database to search for you car if when you return to your spot it's not there.Instead of calling all the tow yards in the city to find your car quickly and provide you the address your car was relocated to and a phone number to call to get your car back fast.