For alternate methods of routing audio through the device, there's a USB port that can play digital audio files straight off of various PMPs and USB thumb drives.
These alternate designs have the potential to allow malware on the device to intercept the card number before it is encrypted by the software running on the mobile device.
Below you can see an alternate fullscreen version of the phone (a hardware reference model, not a device you can expect to buy anytime soon) up and running its browser app.