And the answer is?
The only obvious solution is Flash. Flash has always been all about cross-platform multimedia experiences and user interfaces. People are very familiar and comfortable with Flash, and it is installed on almost all machines in the world. It’s trusted, stable and reliable.
Do we just forget every 10 years what's going on, does anyone remember Flash Generator from 1998? And I still remember the horrible, inconsistent Flash UIs from that era. Has anything changed with Flex?
Via, Bruce Eckel: Use Flex as the UI for Java Applications