For the November contest over at RPG Talk, I came up with a lightweight rule system for using your characters' & society's collective life-force to back a currency. You can download the PDF right here, however there is an interesting curveball.
It turns out I managed to manifest an idea that had been made into a movie several years ago. In Time, starring Justin Timberlake, depicts a world where people with the means may live as long as they want while the average Joe must work constantly to avoid expiring at their 25th birthday.
I was mortified to find out that I had copied the societal system used to drive the plot for a commercial movie, however I suppose I didn't just intentionally rip it off or even copy it 1 for 1 (I still haven't seen the movie... maybe I owe it to j-tim at this point), so here it is. If you do use my made-up currency in your tabletop campaign, please let me know - I'd love to hear your stories!
tl;dr: Slice some time off the end of your life, get money, buy stuff. Need more time? Eat some money. Want to ruin someone's day? Kill the person backing the value of all their money.