Stealth CamUse the Camera app to take photos or shoot videos with the screen off. This way you can save battery and not cause a distraction.
To use, press the sleep button when in the Camera app, then use the volume buttons as the camera shutter button. Also, you can start recording a video using the screen first, then press sleep to continue recording with the screen off.
Bonus feature: Once installed, you can also use the volume buttons as the shutter button in any app that uses the camera. E.g. Facebook.
Available to buy in Cydia for $0.99 from the BigBoss repo.