Up the Sync is a basic Google docs synchronizing program written in Java. It auto-syncs every 5 minutes by default, and can run quietly in the system tray. If the user updates a document on their computer the Google docs version is also updated.
CalDAV sync for Android
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Stopped working on it. Doesn't make any sense to spend more time on it; I recommend e.g. DAVdroid as an opensource and ready-to-use solution on clientside.
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For code look at:
https://github.com/e7o-de/android.caldav