I cant help you as im waiting to order a shield tv, but back when i had my nexus player i remember the app CumulusTV

If you can get your Security cam stream url's you might be able to get CumulusTV to make a live channel out of them, but thats per camera, unless a stream is available showing more than one camera.

If you know the cameras URL use "IP Cam viewer" for Android TV. The UI sucks but I've used it for a long time and it gets updated often still. A few month back is when the develepor ported it to AndroidTV. There is a Chromecast option but I've not gotten it to work well and consistent but the TV app is good.

Not a live channel that I know of but I've not delved into live channels before!