I can think of a few legal and illegal occupations that would find 'Intelligent Counting' extremely useful. 'Intelligent Counting' is a currency-counting thumb ring from designer Yitu Wang that is also doubles as a counterfeit currency detector.
'Intelligent Counting' is designed to work with the technology already embedded in currency to help fight fraud. I'm all for fighting fraud and I could really see this device taking off in banks. Check it out here.