fruux is based on open standards. We’re supporting CardDAV for contact and CalDAV for calendar and tasks synchronization.
Unfortunately no widely supported open standard for “notes” yet. Once there is one, we’d be interested in implementing it.
Another possibility would be to take a look at the VJOURNAL standard (which is not widely supported either though).Joel commented
Should the absence of a standard prevent you from considering this feature?
iOS 7 and Outlook use ActiveSync to synchronize notes. Can your Outlook plug-in be adapted to manage notes? A web interface could be layered on top, like Simplenote.
It would be only a partial implementation that only supports a subset of users, but it would be a feature that would draw some of us.