This "thing" is for generating barcodes, both GTIN13 (known as EAN13 or UPC-A), GTIN14 (encoded as GS1 Databar) and Han Xin Code.
You can input your message, or you can shake your iPhone/iPod. Both work well to get your barcode!
Make sure test them using your barcode scanner, barcode reader, etc. If the result match the message you input, great, you get a good barcode device.
Now, HAVE FUN ~~~ ^_^