The last time I was at Bank of America Stadium, in Charlotte, I noticed someone paying for their food at one of the stands with a chip. I later saw a stand selling them. The way it works is that you buy the amount of money you want with a credit card (only) and you get that amount in chips. They have $5, $10, $25, $50, and $100 chips. You can then use them to buy food at the concession stands and get cash back for the difference. Not sure if other stadiums do this, but this was the first time I have seen it.

I have this extra one for sale if anyone is interested, $7.00 shipped.

Thanks,
Joel