What's my IP simply tells you what your IP addresses are. It displays WiFi and all mobile IP addresses also including internal and external addresses if available.
You can also copy a IP address to your clipboard easily.
By activating the very useful auto-notifier you get a notification if your IP address has changed. A swiss army knife for IT staff.
Also as a special feature you can view your WIFI state (SSID, BSSID, signal strength,.... ) in real time.