Google demoed an offline version of Gmail for the iPhone and Android that works in airplane mode at Mobile World Congress (MWC) 2009 in Barcelona, Spain. The app does its magic by implementing several features found in HTML5, including:
- Database (W3C HTML5)
- App Cache (W3C HTML5)
- GeoLocation (W3C)
The unannounced "technical concept" version of Gmail was demoed on the iPhone and the HTC Magic which runs Android. A YouTube video is available for drooling purposes.