And if you are mostly interessted in High Precision calculations, i would recommend PARI/GP.
No great GUI, but especially for crypto those calculations with 800+ digits precision can come in handy.
I don't know if it is available for NITs, but it would be the first thing i would port if i had a N810.

Bye,
NsN

EDIT:
And for plotting you know about gnuplot, right?