Fastest way to get to camera in iOS?
If you are using iOS 6 (which I am, I can't get iOS 7 on an iPod 4) and the power is on, no matter what you're doing, the easiest way I found was to press the sleep button to put it on standby, press it again to turn it on, find the little camera icon that's next to the "slide to unlock" bar, drag it up to open the camera, and capture your moment. 

Of course, this answer is very conditional: it only works if you have iOS 6, the device is either on or on standby, and you do not have a passcode (if you have a passcode, it makes you type it in before you can use the camera). But it works for me all the time, and I think this would work pretty well for others, too.