Well, that unfolded pretty quickly. I was expecting to provide you with more drama, perhaps a love triangle or terminal illness, but no!
I was bemoaning my lot to my godmother, who said that when she lived in Liverpool in the 70s, there was a babysitting circle arrangement, made up of mothers presumably from the school, or surrounding area - they weren't necessarily friends. What they did was cirulate a list of their numbers. You called around, and whoever was free would babysit - they didn't pay eachother, but used curtain ring currency! You paid one ring per hour, double after midnight, or if you had only black an white telly :) You then used these rings to pay others in the circle when it was your turn. This way nobody owed anyone in particular hours, but you got back what you gave out. It has to be a pretty big cirlce so there'll always be someone free.
I think it's a brilliant idea (though I suppose you could cheat with counterfeit curtain rings pretty easily). I somehow can't see the mothers I know being up for it - those with would presumably pay cash and not have to go mind anyone else's children. However, we all talk all the time about the price of dinner/drinks/movie/taxi plus ten euro an hour on top.