BarkCode offers Doc Halligan's Love Line QR Pet ID Tags. QR code tags that work with or without a smartphone, they help anyone who finds a lost pet contact their owner and back up contacts with a simple camera phone, according to the manufacturer. The tags—made in the USA of lightweight steel—are available in two sizes: The 7/8-in. diameter tags are perfect for kitties and pocket pooches, and the 11/8-in. diameter tags are for pets 15 lb. and over, the company states.