Bridging the Gap: Stripe Notifications
blog.sendwithus.com
blog.sendwithus.com
We've been doing dunning for Stripe from the beginning, support a ton of email types and events, have an iPhone app with push notifications of payments and other important events, payment update pages for your customers to easily update billing info, and we can even send out emails before cards expire.
I think the number of apps you've put it is really amazing and you've got an awesome portfolio; keep kicking ass :)