Our app is currently below the 100mb limit required for download over cellular network when submitting to Apple, but adding the iMessage extension raises the size quite a bit.
Will having iMessage cause the app to get pushed into the download over wifi category or does Apple consider that a seperate entity?
The app binary is considered as a whole unit, including the iMessage extension (or any other extension for that matter). So yes, if your extension raises your app bundle size significantly that may very well take you over the cellular limit.
Are you sharing as many resources as possible by moving things into shared frameworks that both your app and extension leverage? You might want to check out the On-Demand Resources sessions from WWDC last year for more ways to reduce your app bundle install size.
