I was going through the process of integrating Heroku SSO with the addon I am developing and although it was pretty straightforward I was surprised that I couldn't find an existing gem that would add this functionality to Devise.
Once I had it all working in my rails app via a custom Warden strategy I decided that I would extract it into a Rails engine and commit it to Github so that maybe others can use it.
It's still pretty rough and there are a number of things I'm not happy with in the code, but it works for my purposes. I will continue to update and maintain it to keep it working in my projects and if there is some positive response for it in the community I'd love to add more features and clean things up to make it more useful to everyone.
So here is the github: devise-heroku
A few things I don't like that i would love some feedback on or help in fixing: