Work is well underway on Halcyon Calc v1.2. The primary feature for that revision will be plotting of equations. Although we cannot predict a release date yet for v1.2, we have just today plotted our first graphs. To start with, we have plotted sin(X) and 1/X but any equation should work equally well.
As you have come to expect, the interface of Halcyon Calc v1.2 will feature behaviour similar to classic calculators while also taking advantage of the touch interface on the iPhone and iPod Touch. If you have any suggestions for us, please let us know in the forums.