Call me a dreamer, but...how about a cross-application option, something like:
a. There is a application called, say "SafeHide"
b. There is an option/dialog menu in Conversation, Gallery, Notes, (you name it) which could give a user simple (I think simplicity is the point) set of options, e.g "Hide and encrypt this (Message, Pictures, Note, etc)" right there on the spot
c. There is an option to get to those encrypted files from the "SafeHide" (or whatever) interface and:
1. Browse them there
2. Restore them to there mother apps.