Hi!
I proudly present RAXBOY - a small and powerful RPN spreadsheet application running on an Arduino platform (Arduboy).
It's definitely not "Excel in your Pocket" but due to the extreme Arduino/Arduboy restrictions (28k of flash RAM, 6 keys) quite impressing. RAXBOY uses RPN for creating formulae and is at least from the math side very powerful (ie solver, integral, differential equation, function plot, physical constants).
For more information have a look at Github
or see a short video at Youtube.
Kind regards
deetee