It would be interesting if there were a way to run a local client that holds your credentials and does the screen scraping to send back to this API (or others).
Wesabe built our own data acquisition system, first
using downloadable client programs (partially because
that was easier and partially to preserve users’
privacy)
Technically, they could provide a self-hosted version. But that may not be a very profitable business. Also, screen scraping needs continuous updating as the bank's interface changes.
From http://blog.precipice.org/why-wesabe-lost-to-mint/