For those of you who are jailbroken. Snap Tap seems to work on my Iphone 4, 4.0.1 with a older version of mobile substrate installed. 3226 I believe
I really like SnapTap. I have an iPhone 4 and the most current mobilesubstrate. It worked for me for a few hours and when I went into its settings to switch off the shutter sound it stopped functioning. I'm not sure if that was a coincidence or what. Immediately after showing someone how it works I changed the setting and it stopped. It's not officially compatible with the iPhone 4 but I guess it works for some.
I hope he releases a new update soon.