I've been developing the 4-banger I uploaded recently and am approaching a worthwhile scientific calculator. Walter Bonin and I have been working on the keyboard layout and function set and I've been doing the implementation.
The calculator is based loosely on the HP-34c with some of the more modern functions added; it also has complex operations like the 32/35 series but over a much wider range of functinos. Additionall, the device supports superset of the HP-16c integer mode functionality. It is programmable with 500 steps of program memory (every instruction taking but a single step) and 100 storage registers.
Registers and the stack are 16 digits decimal arithmetic. Internal operations are performed in 39 digit decimal arithmetic with an extended exponent range. Statistical accumulations are done in 34 digits decimal arithmetic which should avoid rounding and cancellation problems.
Some special functions are log gamma, beta, zeta and Labert's W – the latter real mode only at present but the former are defined over the complex plane.
Download the sources, installable binaries and the documentation from: