I would have to agree with bjs229, if anti-theft apps can take a picture of the person holding the tablet and send it to you, then a rogue app could do something similar to that, without your knowledge, so even if there was an indicator, it could turn it off. So if you are highly concerned, then as bjs229 suggested just cover the camera with a piece of tape.
Note to everyone, even if you are feeling really euphoric, do not take off your boxers and use them as a "do-rag" while using your Nexus 7.