Android 4.4 (KitKat) is out and brings a lot of new features and changes. One of the changes that it contains is that SELinux (Security Enhanced Linux) now is switched to enforce. This is great news for the user as it improves security. Enforcing rules unfortunately also means that normal apps like the SimpleWebcam app or Dashcam app are bared from accessing the webcam devices. The only way as of now it seems is to use super user rights to access the webcam or turn of SELinux enforcing. Both options require a rooted device.
Another option is to use a custom room which has the security policies set in a way that access to video devices is not forbidden.
For SimpleWebcam refer to this page and use Version 4 if you have a rooted devices with Android 4.4
For the more elaborate Dashcam app found in the app store you will be prompted should a rooted device be required.