Under Gnome (and Unity) Evolution Data Server, a part of the Evolution PIM suite, provides similar functionality for task, calendar, and addressbook information. It is also used in Nokia's Maemo platform to store contact data.
I am not aware of anything offering similar functionality for e-mail data, but Desktop Couch could be used in that manner. The present lack of a standard data schema for representing e-mail as CouchDB documents would make interoperability between different applications using it as a data store difficult, however.
Under Gnome (and Unity) Evolution Data Server, a part of the Evolution PIM suite, provides similar functionality for task, calendar, and addressbook information. It is also used in Nokia's Maemo platform to store contact data.
I am not aware of anything offering similar functionality for e-mail data, but Desktop Couch could be used in that manner. The present lack of a standard data schema for representing e-mail as CouchDB documents would make interoperability between different applications using it as a data store difficult, however.