@larand I used the PMarc app for a bit (http://appshopper.com/link/pmarc-app-the-premium-tweetstorm-tool-for-twitter) but an API would make it easier to post long-form here as well as there without worrying about length and format.
Also, it's in twitter's benefit as it would solve longform completely and they would be in total control of how tweetstorms work.