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.