Excellent thread - thanks!!
I hacked together a quick Google Docs spreadsheet to play with the numbers for my own uses, and I'm in the process of creating a small website with an SSS-style calculator on it.
I'll keep you posted when it's up.
Did you see this,or is it not SSS-like enough for your tastes?
http://xzist.org/amazing-bitcoin-retirement-fund-calculator/You're welcome to re-use the source.