i wonder on which smartcards i can actually run javacard? afaik it requires the "open platform" OS, but: which USIM-cards for mobile phones today (especially in germany) do actually support this?
As far as I know all SIM card produced during last ~10 years are able to run java. The problem is that you need code can be obtained from the card owner, i.e. the carrier. But carrier will not give you this code unless you are the carrier's partner...
Probably the following links can help you.
http://forums.techarena.in/software-development/1353925.htm
How to programmatically load a Java card applet ( a .cap file ) using Visual C++/PCSC