Why Did Apple Ban iPhone / iPad WiFi Scanning Apps?
Official Answer: Because there are “no published APIs that provide the ability to manipulate the wireless connection or the show level of information regarding the wireless connection”.
English Translation: Apple has not documented a way for developers to collect RSSI, Noise, Channel, and other information usually displayed by WiFi Scanners.
iOS 4 WiFi Scanner Apps
Stumbler iPhone WiFi Scanner App
Info from Stumbler / “iphone-wireless” website below.
Stumbler lets you view the wireless networks in your area. While right now Stumbler only handles 802.11 networks, soon you should see Bluetooth and GSM capabilities as well. Stumbler is still in a early Alpha stage, but it is fully functional, and pretty stable.
Raw 802.11 packet capture (monitor mode)
Screenshot of Alpha Version of Stumbler App
iOS 5 Broke WiFi Scanner Apps that Worked on iOS 4
In iOS 5 a few items changed causing apps that worked on iOS 4 to stop working. The developer community was able to make changes to get their apps working again but iOS 5 scanning feature only works on jailbroken devices.
My fear is that Apple doesn’t want others (ahem..Google) using their large iPhone/iOS user base to create/improve their WiFi position database that would compete with Apple’s WiFi location database so they are in no rush to provide this capability. Or it could just be that they have many more important features that need attention.
My hope is that Apple will provide a documented way to get needed information on iOS like they have done on Mac OS.