New day, new update in Cydia: SnapTap. This tweak lets you take pictures and videos using the iPhone’s volume controls and wired headset buttons. SnapTap gives you extra options for taking pictures beyond small and annoying touch buttons. Compatible with many camera-enabled applications.
The new update comes with full support for iOS 4 and iPhone 4.
You can buy SnapTap from Cydia Store for $1.49