Photos

Albums and photos. The photo bytes are the node's blob; EXIF is a facet of its own.

Contacts

Address books and their contacts (vCard 4.0, RFC 6350).

Google Calendar sync

The calendar app's link to Google Calendar: the account, mirrored calendars and their event joins.

Calendar

Calendars and their events (jsCalendar, RFC 8984). Availability is a facet of its own for free/busy sharing.