Wi-Fire USB Antenna Promises Access up to 1,000 Feet
The device is a directional high-gain antenna. It works with any 802.11b or g access point and can work at up to three times the distance of an internal AirPort card by itself - up to 1000 feet away from a base station, according to hField.
The Wi-Fire measures 3 x 4 x 3/8 inches and folds up when not in use. You can perch it on a laptop screen while you're using it.
Software included with it - the Wi-Fire Connection Manager - reveals all available networks in the area.