Yes, you can use your iPhone barcode scanner to import ISBN numbers to EYB. There are several different versions available but I think they all work more or less the same way. You scan the barcodes into a text file on your phone then email it to yourself. Then copy the list of ISBNs into the Import Books feature (link in left navigation).
I suppose you could just copy the ISBNs into Import Books on your phone though the text on EYB would be rather small.