AirPort Utility

As described in the iTunes App Store:

Use AirPort Utility to manage your Wi-Fi network and AirPort base stations, including AirPort Express, AirPort Extreme, and Time Capsule — right from your iPad, iPhone, or iPod touch. See a graphical overview of your Wi-Fi network and devices. Change base station and network settings, or manage advanced features such as security modes, wireless channels, and more.

AirPort Utility works with all Apple 802.11n Wi-Fi base stations, including AirPort Express, AirPort Extreme, and Time Capsule.

• See a graphical overview of your Wi-Fi network
• Get information about your connected Wi-Fi devices
• View and change network and Wi-Fi settings
• Restart or restore a base station, or update the firmware on a base station when available
• View or update passwords for your network, base stations, or disks
• Easily access network information such as IP address, DNS servers, and router addresses
• Manage DHCP reservations and port mappings
• View status or error messages for your base stations