Is there a Cydia tweak that gives the camcorder its own button?
This is a four step process that takes less than 3 seconds for me on iOS 6 - so I don't know if anyone's going to tweak this in jailbreak.


Press the sleep wake button to lock the screen (or wake the screen if the phone is off).
Press and swipe up on the camera icon on the lock screen.
Decide if you want video or photo and examine the toggle where you initially pressed the camera icon.
Tap the toggle if the camera isn't in the mode you prefer.
Tap the record button.


If you take 3 minutes to practice this, see if training your brain to know it only has to track two places on the phone speeds this up fast enough to avoid needing a dedicated button. The lock button and a very small portion of the screen are the active targets, so you might be able to optimize your speed to start recording knowing that you can start recording as fast as possible and then trim the clip later once the recording starts.