Iphone app that stores affinity/discount cards, displays barcodes for scanning?

Factual Questions
1

An acquaintance of mine showed me an Iphone app that he uses to store all his affinity/discount cards (CVS ExtraCare, Harris Teeter VIC, etc.) and it displays the barcodes so the cashier or the self-checkout machine can just scan the face of the Iphone.

I can’t remember the name of the app. Anyone know of a good one for this purpose?

2

I’m surprised that works at all. I thought most barcode scanners needed contrast in terms of reflectance or absorption, not luminance.

3

CardStar is one such app, although I’ll bet there are several.

4

I use Cardstar, but I’ve had very little luck getting the scanners to read the codes. A shame, 'cause it’s a great idea.