When the camera's completely switched off, hit the power button and you'll go straight into camera mode which lets you shoot immediately, then about half a minute later the interface seamlessly goes back to smart mode, which is when you can hit the back or home button to toggle the Android unlock screen (though we'd rather go straight into the home screen).
ENGADGET: Nikon Coolpix S800c hands-on: a closer look at the Android camera (video)