
WiFi Key Recovery (needs root)
wifi-key-recovery
About App
** You need root to use this application. ** You need to have connected to the network in the past. ** This app cannot "hack" into an unknown/new network. I cannot help you with getting root. Have a look at http://forum.xda-developers.com for that. Have you ever forgotten the password of your home WiFi network, or the one you setup for your parents a few months back? This application will help you recover the password of a wireless network you have connected to with your device in the past.
Developer info