Gallery application replacement for adding text based Photo Notes
There are a number of photo apps that will let you edit exif data on the android.  This one specifically does the data: https://play.google.com/store/apps/details?id=com.teapps.exiftageditor, some do other pieces of editing, some sort your files for you, etc, etc.  Take a look around for one that works well with your particular image work flow.

Wikipedia has a nice roundup for PC/desktop meta data editors here: http://en.wikipedia.org/wiki/Comparison_of_metadata_editors. Your choice will of course depend on your PC, budget, and needs.