How to Tape Over Your Cameras on Your Devices

The Prime Minister of Australia wears an Apple Watch. Does this pose a problem? If someone lifts your thumbprint from a really good photo, does this give them an easier hack into your mobile devices? And the second question is, do you have problems with thumb prints on your watch? Because I can handle thumb prints and greasiness on my phone, but I imagine it would be more infuriating on something like a watch.