I heard about Red laser barcode scanner, but did not try. The problem with EAN/UPC (grocery) symbols is that they are optimized for laser scanning - flat bed, one laser pass, poor light conditions etc ... QR, 2D barcodes are optimized for imaging where a complete (or incomplete) picture is analyzed.

"Barcode Reader" on Android, which uses the zXing library, worked for me. (I don't know how the iPhone app works, but Barcode Reader continuously takes pictures until it recognizes a barcode. It seems to work quite reliably.)

RedLaser from Occipital (a techstars company, I think) is in the iphone app store.