This video was produced using v1.0 of Halcyon Calc. Since then, version 1.3 has been release with some features not seen in the demo video:
The page control below the period button has been removed due to accidental clicks (you will actually see this happen a couple of times in the demo video).
The ability to create simple programs which can execute a sequence of operations has been added.
Programs can be created which take arguments from the stack and can become custom operations which you can use within expressions. If Halcyon Calc does not have support for the operations you need, you may be able to add them yourself using this feature.
The ability to plot expressions on an X/Y coordinate space
iPad support.
Probably a new demo video will be produced in the future but for now this video is still fairly representative of what it can do.