DB48X is a modern scientific calculator in the spirit of the Hewlett-Packard HP48X, featuring a complete, from-scratch reimplementation of the Reverse Polish Lisp (RPL) programming language. The firmware is initially designed for the SwissMicros DM32 and DM42 calculators. In other words, it is optimized for physical hardware that you can keep in your pocket. There is also an iPhone version if you want to run this on your phone or display graphs in colour.
You can try the calculator firmware directly in your browser by clicking on the following image: