This QuickerTek WiFi transceiver from QuickerTek is supposed to improve your MacBook Pro WiFi signal by 100 percent—meaning you can wander twice as far and still be able to access the network. It works by connecting a wire to the internal antenna out through the case to the outside, to an external antenna which sits on top of your screen. The downside is that the 27dBm transceiver is AC powered, meaning you're going to have to find an outlet at Starbucks to plug this into if you want get better reception.
Fairly useful if you usually stray towards the edges of WiFi reception at home or at work. Although at a price of $200, maybe a DIY Pringles can solution would be better?