Problem:  So your paying AT&T plenty of money to use their slow, spotty, 3g network.  AT&T and Apple have gotten together to tell you what apps can and can NOT use 3g data.  One of your apps that you need to use anywhere is only allowed to access the internet via WiFi.

Solution:  Jailbreak your iPhone and install VoipOver3g via Cydia.  VoipOver3g will trick your apps into thinking they are using WiFi, when really only 3g is available.  To tell VoipOver3g which apps to allow you need to add the bundle identifier to the /Library/MobileSubstrate/DynamicLibraries/VoIPover3G.plist on your iPhone.

How to find an applications bundle identifier:

• ssh into your iPhone
• cd /User/Applications
• find . |grep appname
• cd into the long folder name
• cd in appname.app
• nano Info.plist
• find <key>CFBundleIdentifier</key>
• key should be just below it: <string>com.vnetcorp.sipphone</string>
• nano /Library/MobileSubstrate/DynamicLibraries/VoIPover3G.plist  and add to list

Simply add that string to your /Library/MobileSubstrate/DynamicLibraries/VoIPover3G.plist, reboot the phone, and that application should now be able to access the internet over 3g!