I maintain an open source project called Blackbox which makes it easy to store GPG-encrypted secrets in Git, Mercurial, Subversion, and others.
I've written up my ideas for where the project should go in the future, including renaming the commands, change where the keys are stored, add a "repo-less" mode, and possibly rewrite it in a different language:
https://github.com/StackExchange/blackbox/blob/master/Version2-Ideas.md
Feedback welcome!
Tom