@jens
What is exactly your requirement?
1. Do not let Google, the company, to get their hands on your calendar/contacts? Implies defense against their backend; or
2. Do not ever touch an app created by Google? Implies defense against their front-ends;
3. Both.
Which is it?
@FailForward @jens what about defense about their privacy policy. The security of their backend is likely not a problem, but the way they handle data is.