eMail query-command to use vCards in mutt and Vim.

vdirsyncer is a command-line tool for synchronizing calendars and
address books between a variety of servers and the local filesystem.
The most popular use case is to synchronize a server with a local folder
and use a set of other programs to change the local events and contacts.
vdirsyncer can then synchronize those changes back to the server.

• vdirsyncer @ GitHub.

Secure Data Sync.

Secure, end-to-end encrypted, and privacy respecting sync for your contacts, calendars, tasks and notes.

Easy to use and open source - it seamlessly integrates with your existing apps so you won't even notice you are using it!

• EteSync server @ GitHub.
• etesync-dav @ GitHub
  is a CalDAV and CardDAV adapter for EteSync.