Idea: Let people donate the processing power of their billions upon billions of personal devices out there, like the SETI/Folding@Home projects but for general

Idea: Let people donate the processing power of their billions upon billions of personal devices out there, like the SETI/Folding@Home projects but for general distributed computing, give them some kind of e-currency for that, and establish an economy on based that currency. You can run whatever you want (up to the storage/electricity limits I allow) on my computer/phone when I'm sleeping, give me eBling, and charge me eBling for web searches etc. Make it so that donating 12 hours of a mid-range phone's CPU would pay for 24 hours of web searches, or something like that.