An app that claims to track your banknotes after you have spent them.

http://wheresyourmoney.com

I expect in time, banknotes will get RFID tracking built in, but until then, you’ll have to type in the serial number.

Have you ever wondered where your money goes once you spend it, where it's been or who had it before?

No. No. No.

I, quite literally, couldn't care less.
Why would you want to know?

Curiosity. The problem is though as far as I can tell there's no actual tracking of notes, it relies on the people who get 'your' money going to the web site and inputting the numbers and their location. Somehow, for the vast majority of the money in circulation, I can't see that happening.

Didn't I read somewhere that we might be switching to the Aussie style plastic bank notes soon.
They're supposed to last much longer, be harder to forge and be water proof. Although they do cost more to make.

Weren't high denomination Euro notes proposed to have RFID before they realised it would make it a muggers paradise? They could simply scan for people with a sufficient currency count to trigger the mugging.

I do not want to know or I'll start washing all money and use alcoholic gel all the time :S

It's not where the not you have is going next. It's where t's been before you get hold of it that's the worry.