Ok, may have found the primary culprit for this and it's not
the ipCAM app itself.
Putting an iPhone up against a window as a webcam on a sunny winter day means the phone is in full sunlight for a few hours: enough time for the phone to get to a high temperature and stop working. The high temp screen comes on and stays there until the unit cools enough to continue. However, like any other interruption, the running app is now in the background or stopped. I found this out when home on the weekend and able to get to the iPhone after it had stopped responding.
I've since put some reflective insulation between cam and window and the device is a lot more stable. I currently scrape the app webpage every 15 minutes for the image, logging any failures. Over the past few days I've noticed a few times when the app doesn't respond but then comes right later. For example 10:00 success, 10:15 fail, 10:30 success, 10:45 success ... That's acceptable for my purposes
So the moral of this story is to remember placement and device operational environment as well as the software itself!