Feature request: In App reference photo

When live viewing a camera, I'd love to be able to snap a "reference photo" for that camera, (saved in app, not in the phone's camera roll) then be able to while in live view to flip between live view and the ref photo to see what changed. (or view viewing a camera at night (dimly lit scene) see the reference photo of the same scene in daylight to know what's where.)

(when taking a new reference photo it overwrites the previous one)