Another approach is to use an IP Camera that has some Input/Output connections. I have 6 IP Cameras and all but one have an output that can trigger a device when the camera raises an alarm (configurable). My dome cameras are all Hikvision and they have both an input (to trigger recording) and an output (to trigger something upon condition met). If you hook up one of those dry contact sensors, your generic IP Camera can now trigger events in ST without any additional software. Even one of my D-Links (low cost motorized IP camera) has the IO. I have not tried this so there may be unforeseen issues with this setup.
Biggest issue is that unless the camera has a PIR sensor, the image based motion triggering is very prone to false alarms.