Roman numerals. Or hex. Random per topic isn't all *that* bad.. but.. meh.
As for pi-base. That is freaking awesome. I think I'll write something to do that. Only thing is, I need to figure out how :s
Anyways, we can use 22/7 as a good estimate for pi. So, the least significant digit represents 1, the next 22/7, the next (22/7)^2 = 484/49? Oh gawd. There is another problem, in that we have to make exactly 22/7 digits. How you make a fraction of a digit is beyond me.
EDIT:
Apparently it's
possible. It appears to use the digits 0-3, which is really 4 digits.. Oh well. We can do that I guess. And then everything else I said is the same. Coding is another story...