You can easily close or open the webcam at any time. This may not work if you have a screen protector. The sliding part can fall off, but works well when placed horizontally. So it's probably not practical for tablets, as you might also need to rotate the screen vertically. Also not suitable for rear cameras of Samsung phones or tablets.
Laptop Webcam Cover Slide: Ultra Thin Round Hole Camera Blocker for MacBook, PC & More (3 Black + 3 White)
11 Review
Shutter Logitech Protect Privacy Security
10 Review
imluckies Webcam Cover Slide - Slim Metal Camera Cover for Laptop, MacBook, iPad, iMac, PC - 6 Pack, Ultra-Thin 0.023 inch, Privacy Protection
12 Review
6 Pack Webcam Cover Black - NanoTech Reusable Adhesive Protection for Laptops, Smartphones, Tablets, Desktops - Works on Any Electronics Surface - Safeguard Your Privacy
11 Review