Curated list of open-source Java Card applets and related applications for cryptographic smartcards - ermuur/javacard-curated-list ...

And Python itself is easy and powerful, and cross platform. PythonCard uses the wxWindows widget set and I have successfully run that on Windows, Linux, and MacOSX.

With PythonCard there is no learning curve, you just start drawing widgets and screen layouts and it magically generates the Python code for you.