Yes and no. RaceChrono most parts runs without Internet connection, but sometimes it’s needed. Usually the Internet connection is so rarely needed, that you will be fine tethering to your main phone whenever needed.

• App startup (RaceChrono Pro for Android only): License check from Play Store is done on app startup every one month, and it requires Internet connection.
• Track library downloads: If you want to browse or download a new track profile from RaceChrono Track Library, you will need Internet connection.
• Map tiles: If you want to see map tiles in the analysis screen, you will need Internet connection. The map tiles cannot be pre-loaded.