Damn kids, always on their tippity-tappity phones!
So this was actually pretty wonderful. I have not seen this kind of setup for a horror game before - not so much basing it around phones, but more the outside look of the house, with a camera swooping from room to room to show reactions ot the conversations happening on the phones. It worked wonderfully (and a few camera swoops are pretty excellent - I like the detail of zooming by a Jack-O-Lantern, for instance!). I especially like that the game does make you have to tap buttons in order to type on the phone - it's small and subtle, but it does add just that tiny extra layer of immersion.
The buildup is super nice, and while I can see the payoff splitting the audience in the middle depending on wether they expected something more traditional, I for one got a good laugh out of it. And while the "First Person Mode" is a pretty neat look at the house, it doesn't feel like that much of a 'reward' to be perfectly honest.
If I have to nitpick, I would say that on occasion, your dialogue choices, as displayed by Emojis, are not very indicative of what the character actually ends up saying. I didn't always feel like I knew what response I was going to give, and sometimes they were too small for me to even really see what they were. So perhaps that's worth some consideration.
Still, enjoyed the Hel(l) out of Helmouth Halls for sure.