AirPort Utility for iOS
Apple has released AirPort Utility for iOS. A free app that allows you to setup, configure and test wireless networks utilizing Apple's Airport base stations or Time Capules.
Interesting that when Apple is phasing out the use of "Airport" in favour of the industry standard Wi-Fi (For example, the wireless network menubar used to say "Turn Airport Off", as of OS X Lion it says "Turn Wi-Fi Off"), this app is still called AirPort Utility.
iOS5 is required to use Airport Utility.