I’m not sure if this kind of device is right or not, but WiFly-City claimed to be able to ‘unlocked’ most of locked WiFi Network and providing you up to 10-times higher transmission distance so you can actually let your PC/laptop sniffs for WiFi network in the range of 2 kilometers. I certainly won’t believe it until I’ve tried it myself. However, it would be interesting to be able to get a free WiFi network access where you’ve no need pay a dime for it.
You can find the detail at IPmart, but I’ve no idea if unlocking someone’s locked WiFi network is considered as thief or not. So please bear in mind that using WiFly-City is purely at your own risk.