This is a really geeky app! You know USSD? They're the codes you can type in to your phone to send messages back and forth to the networks. You've probably seen something like *#147# to display the last caller.
My second app presents a series of buttons which call the USSD commands - so you don't have to remember if it's the HLR or VLR which is queried by *#103#.
Useful, I know....
You can download the app by scanning in this QR code.
The majority of these codes only work on phones with a Vodafone UK SIM who are on the Vodafone UK network. I've no idea what the codes do on other networks.
Sadly, Android provides no native way to capture or interprate USSD responses. Please star the feature request if you're interested in seeing this in future versions of Android.
One last thing - this app was neither designed nor approved by Vodafone UK. It has nothing to do with them!