potluckman:
I've done some research..... Android is notorious in regards to background processes. Furthermore, OS developers see it as a feature, not a bug. Why? It extends battery life, it prevents computer-illiterate phone users overloading the phone's RAM etc. etc. That way, phone mfrs can get away with cranking out subpar hardware.
The consequence of that approach is that the OS (unlike a desktop one!) never gives you any guarantee your app will be left peacefully running in the background.
Theoretically, your specific Android device (to be precise, the firmware, since these are replaceable) might have some settings designed to change that behavior. There's significant variety among firmware versions, so unfortunately, I can't provide you with reliable tips here.
You might want to look for those settings on your devices, but tell you what - those aren't guaranteed to work, either! I'm saying all this so you understand that the odds are stacked against you.... don't get frustrated.
Eventually, I've had some luck with TinyCam - but again, I had to go through some hoops before I got it to work.