What is a good strategy for accessing an API which is limited to a static IP Address from Heroku?
Ok so after a bit of research I've discovered the best way to do this currently is indeed with an AWS US East EC2 instance running some sort of proxy. I've gone with linux/nginx.
I've also learned there is a Heroku add-on currently in alpha stage of development that will handle exactly this requirement. If you'd like to test it, get in touch with Heroku support.
You can also use the Proximo add-on to get a static outbound IP address via proxy without any of the maintenance headaches.