The Flatenna is effectively an enhancement to your existing antenna. Its a parabolic reflector which beams the back emissions from the antenna into a forward beam. This will extend your WiFi/WLAN range.

The Flatenna is a pseudo parabolic reflector made from silvered board containing an aluminium layer. The Flatenna provides a 7db boost in signal in one direction. These tests were carried out with a 5dbi 5/8 wave stub antenna and 2dbi 1/4 wave stub antenna. The Flatenna is intended for indoor use only.

[Via Tritium]