I usually don’t like to link to competing projects, but this seems to be only for Linux so I think I can link a similar one (as far as I can understand from the screenshots) for OS X and iOS: http://acqualia.com/soulver/
looks interesting, I wonder if it can be ported to Windows, where I have to spend my working life :-(.
For something even more sophisticated and Mathcad-like take a look at SMath Studio: http://en.smath.info/, unfortunately only free as in beer.
I have been looking for something like this for a while, I find software calculators to be woefully inadequate for anything beyond the most basic math. Will definitely check this out!
Neat. I'm a regular Sage user, and this seems to be an interesting tool for when I don't require the full power of that tool and just need to make some quick calculations.
Apropos nothing: I'd really like an alternative to Sage for light linear algebra work. In particular, I'm not in love with the way Sage interacts with Python.