Borderline with the "off-topic", but anyway (I did not know were to put it):
For those who do not know Qalculate!, it is a powerful calculator software that have unique units handling capabilities not present on other apps.
AFAIK, KDE SC can be compiled to use Qalculate! libraries for the calculator runner and there is also a useful Qalculate! plasmoid available.
But the project maintainer have problems to push this really great app into the future:
[Qalculate! forums on SourceForge]future of Qalculate!
I think that even by participating on that thread you will help the project... but of course if you can code...