The description of the "Presence Video Security" app in the App Store says (emphasis mine),
"You've got an old smartphone or tablet. It's sitting there, doing nothing. Why not put it to work? Let the free app Presence watch your back. Get it today, and you've got a home security camera system in less than 5-minutes. Download Presence on BOTH your primary smartphone - the one you use every day - and your old smartphone or tablet. Position the old device in the direction you want to watch and secure. You'll get recorded video alerts when something happens. You can even see what's happening remotely from anywhere."