The seatbelt cell phone holder is designed to be attached to your seatbelt and provide easy access to your cell phone. Made of nylon, it comes with a pocket for your cellphone and another for your headset. It is also removable (Velcro) so that it can be attached to other straps (like the one on your travel bag).
The seatbelt cell phone holder is available for 7,90€ (just over $10 USD) from Portuguese site D-Mail.
Source: The Uber-Review