My personal favorite bar code reader is RedLaser:

http://itunes.apple.com/us/app/redla...474902001?mt=8

You could also consider Google Shopper, which shows a price search for the scanned product on Google Shopping:

http://itunes.apple.com/us/app/googl...416091721?mt=8

Amazon.com also has a similar app:

http://itunes.apple.com/us/app/price...398434750?mt=8

All are free.