Advanced Custom Fields add-on: Front-end Editor
This is an add-on for WordPress Advanced Custom Fields plugin
The add-on allows admins to edit text fields, textareas and wysiwyg fields from front end simillary as you would edit a google doc.
Plugin is in early stages, code needs a bit of cleaning, but it does its job and doesn't collude with other plugins.
P.S. it also works with OPTIONS page fields, in the LOOP, with repeaters and flexible content:
Add-on author: Audrius Rackauskas @ Horion Digital, Ltd
ACF plugin author: Elliot Condon