Like many people, I have quite a few membership cards attached to my key ring. Recently, I discovered that that the bar code on my Food Emporium card had rubbed off enough to be illegible to bar code scanners and barely legible to the naked eye. So I photocopied the code on my wallet-sized card, taped it to the key card, and covered it with clear library tape. Voila! She scans again. But I do hate the extra thickness the cards add to my keyring.

Today I discovered an iPhone app called CardStar that might help me with that problem. I got an iPhone to reduce the number of gadgets that I customarily carry around, and CardStar promises to help with keyring heft. Quite simply: it allows you to enter in the number on your loyalty card and it generates a bar code on your screen that can be read by a bar code scanner. The app’s database contains a number of common vendors and organizations found in the US, Canada, and the UK, but you can also enter in numbers for organizations that aren’t in the database. For stores that are in the database, there is a locator that will show you the nearest location on a Google map. (It revealed ten Duane Reade locations in the general vicinity of Union Square.)

In addition to lightening my keyring, CardStar also lets me keep various numbers on file that I don’t normally carry around (for example, frequent flyer numbers and reward cards for places that I visit infrequently). I know, I could just keep a list of numbers in the Notes app, and I could just enter “Duane Reade” into Google Maps myself, but what fun would that be?

CardStar is currently free from the iPhone app store. Eventually it’ll cost 99 cents.