From the ‘so simple why didn’t I think of it’ category
A friend of mine pointed me to this brilliant post (via iPhone Central)
The concept is simple; Scan the front and back of all your barcoded membership cards, and carry them around in your iPhone.
To test it out I went to the local hardware store and asked the girl
behind the counter if she could scan the barcode from my phone. The
first look I got was pure amazement. To her the physical card was
transformed into a picture on a shiny device. On top of that the
barcode was scanned successfully. The result; a slightly confused girl
and a happy me.
My take: I’m going to try this on my library card and see if this works on my Palm Pilot T|X.
bradgrier.com 
From the “so simple I think there may be more to it than that” category: I can see using those promotional cards: grocery cards, airmiles card, store discount card, they are an absolute pain to carry around with you. And truly for no other reason than for them to pretend to give you a discount as long as the number is clear they should take a scan off a phone.
But as for the other cards like the swim card or library card, call me old fashioned but I run the risk of losing things lately and to lose it all at once in a itouch/ipod/palm would be just a bit of a pain not even counting the ID theft aspect. As for the cards that count, they aren’t all in one spot for me right now so maybe I lose my swim card, no biggy.
Nice idea for the other stuff though!
Takonme
May 13, 2008 at 11:18 am
I don’t have an iPhone, but if I did, I’d do this. Besides, worst case scenario, you can just read the number to them and they can enter it by hand.
Adam Snider
May 13, 2008 at 12:12 pm
@Takonme, @Adam,
Both good points. Losing the device would be trauma enough, but losing the cards stored on the device would be worse.
I can’t see this working for Credit Cards or Debit cards though. They need a mag-stripe…but for anything with a barcode it should work.
Must remember to test it.
bgrier
May 14, 2008 at 9:59 pm