Privacy Protector app will allow you to enable/disable basic functionalities such as camera, microphone (as of now) and do more a lot in future updates.

The application will require device administration rights to disable camera functionalities.

It does not contain ads and will not be added in the future updates too.

It may also contain a beta feature of disabling your volume buttons, will be releasing a stable version in the next update.

If you are an android developer, you may take a look at the code in GitHub

https://github.com/pbkn/privacy-protector

This application does not spread/infect your phone with malicious apps and is completely offline.