Network Toolbox may be the best network app on in the Apple App Store. It is designed for both iPhone and iPad and if you are an enterprise IT professional or just a technology enthusiast it belongs on your iOS device.
The Toolbox contains a suite of 32 tools that will help you analyze networks for configuration. It is also helpful in security or just general awareness of the networks you are on. Capabilities include WiFi network IP scanning, Port scanning, Morpheus and Shodan search, Map Search, NS-Lookup, Ping and Trace Route. There are also Bonjour and Bluetooth scanners.
I've found the scanning to be faster than other similar apps in the App Store, which is important when enumerating large networks. There are also handy security tools that let you test for standard default passwords on many common network devices. This is a nice feature for people with networks to secure.
Maybe the most important feature is how easy it is to use. If you have the skills of a network engineer or if you are just a hobbyist you will find it a breeze to operate and easy to push to its limits. If you are new to concepts there are great videos and help features that will walk you through what you are doing.
Find it on the Apple App Store by searching for NetworkToolbox