How do you know? There is a card reader and scanner attached to the iPod, with a USB port on the bottom. Article says nothing about the operation of the device. Internet purchases are not done on a portable device in the hands of another person.
But if you are gullible enough to think these devices are foolproof and secure, then make your purchases with them. Having your credit/debit card info stolen is the first step in identity theft. I would rather use a fixed point of sale device than a portable hand held device.