Here’s how Google Fi will work with iPhones
theverge.com"you should know that iPhones won’t be able to make calls or text over Wi-Fi, use visual voicemail, or be used as data hotspots outside the US at all"
That's worse than a standard T-Mobile plan, which I'm currently on. I don't see any reason to switch.
Unrelatedly, The Verge's link to the iOS app goes through something called "go.redirectingat.com", which fails because it's on my tracking server blacklist. Seems pretty sketch.