OpenHBCI -- the first free client-side implementation of the HBCI
specification.

HBCI is a bank-independent homebanking standard used by many German
banks. This publicly available protocol describes communication,
authentification, encryption, and business transactions taking place
between a homebanking applications and a bank's server. OpenHBCI
provides an object oriented library implementing the current
client-side HBCI specification. The library is written in C++, with C
wrappers also available. OpenHBCI provides the application programmer
with a high-level abstraction of almost all business transactions, so
that all HBCI details are totally encapsulated and do not need to be
bothered with.

WWW: http://openhbci.sourceforge.net