iPhone volume boost (Jailbreak only)

• Download this file
• Extract the contents somewhere convenient.
• SSH into your iPhone through WinSCP or cyberduck.
• Navigate to the /System/Library/PrivateFramework/Celestial.framework/ folder.
• Locate the file RegionalVolumeLimits.plist and rename it to RegionalVolumeLimits.bak.
• Copy over the RegionalVolumeLimits.plist file you extracted in step 2 to the iPhone's /System/Library/PrivateFramework/Celestial.framework folder
• Set permissions to the RegionalVolumeLimits.plist to 0777.
• Reboot the iPhone.
• Dance.

From http://modmyi.com/forums/file-mods/642471-volume-boost-3-0-a.html