The camera is definitely being accessed since I see the camera lens moving every once in a while (once every 30 mins up to once every 15secs),and due to a hardware imprecision the lens touches the glass of the camera, which results in a very distinct click sound. Pictures don't show up in the gallery, but apps like Cerberus can do that easily without leaving any hint besides on my phone the click sound.

thanks, lots of apps there. I was looking for something like a task manager which shows the active task that just accessed camera functions, or a method to restrict camera access and show which tasks are asking for it. I have cerberus and wheresmydroid installed and could imagine them to stalk after my pictures, or potentially a virus.