Camera With Wifi And Gps

What iphone 3Gs functions wont work having only WiFi access?

I currently use an ipod touch with a Bell MiFi device to connect to the internet away from home, and now I want to buy a new iphone 3Gs to use exclusively with WiFi in the same configuration. What functions of the iphone wont work without a cellular connection? Will the GPS/Compass/Camera or any other iphone specific feature no work with only WiFi?
Thanks… Jason.
Yes I have wifi in my car. Thats what the MiFi does.

GPS is working fine on WiFi, but is there any WiFi signal in your car while you are driving in the highway ? =D

Most applications are working fine on WiFi (only).

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