Dont dither,take the shot!
There is a similar/same application for sale over here John, about £100 ish I think though.
Looks like it bulks up the rifle /scope a bit though.
I wish I was half the hunter my dog thinks I am
"looks' good on their promo video. but I think the recoil on a deer rifle would give dodgey footage. And I dare say the video on their site was filmed through a new phone/top optics on a nice day. Not a scratched iphone on a wet day stalking in low light. Nice idea though