Arduino + magnetic strip reader + paypal = payment processing machine?

It should be the same as when you're typing your CC info into paypal to purchase something in the situation where you don't have a paypal account. After you've typed the card #, exp date, security #, etc., the web form just simply sends that data to paypal. Paypal makes an CC reader and app for smart phones for this very purpose. I guess I should just use a smart phone with a WiFi connection instead. what do you think?