My dad has an old Palm Centro on a grandfathered plan that he won't get rid of until the phone dies. He wants to get an unlocked Pre 3 to use as a WiFi-only device until the Centro dies. Besides the phone functions (calls, IM, MMS, etc) are there any other features that wouldn't work using the Pre 3 WiFi only (i.e. GPS)? Will the device even work WiFi only?