Well, maybe you take a look at the examples here
Versatile WebCam C# library
] or WebCam Fast Image Capture Service using WIA
] and just check if the device is availale and able to capture. If you do this frequently you know when another application is using the webcam because the access should be blocked for your application - maybe not, if concurrent usage of webcam devices is possible, as far as i know it's not. do the same for mic, clipboard and screen and post your security suite here. i am very intrested in this for your concerns are totally reasonable. contact me on success.