Does Sky Guide work without Wi-Fi or cellular service?

Yes. All the information in Sky Guide is self-contained so access to the internet is not required for full operation. If you are in an area without Wi-Fi or cellular service, you may find that geolocation can take a little longer, but GPS will eventually determine your location. For devices without GPS like the iPod Touch and Wi-Fi model iPad,  you may need to select a manual location in the Main Menu > Location > Manual Location.