There will always need to be some sort of program or service running on the computer for the iPhone to communicate with. There is the possibility that the video capture on the camera could be turned off until the iPhone connects. Other users have asked for that capability, and we may add it in a future version of iCamSource.
EDIT: Just a note that motion detection requires the camera to be active, so the feature described above would not allow motion detection or push notifications while the camera was inactive.