UPDATE: Google just made it official via a blog post. Here are the list of devices that are eligible:
Despite its merits and reasonable plans, Google’s Project Fi is restricted to only a handful of devices. Today, a report by Droid-Life indicates that Google will announce Project Fi compatibility for more devices including iPhones, albeit in a limited capacity. A broken embargo post from BGR (now deleted) details some upcoming plans from Google regarding Project Fi. While there’s no mention about an official rebrand from Project Fi to Google Fi, more devices do seem to be joining the Fi family.
At the moment, Project Fi only works on Pixels, Nexus devices and a handful of phones from LG and Motorola. A data-only SIM can be used on any device, but that still has restrictions. It seems that Google is planning to announce further official support for more devices. It is reasonable to assume that devices from Samsung, OnePlus, as well as brands already working with Fi in Motorola and LG. Apple fans can rejoice as it appears that Google is adding official support on Fi for iPhones, at least in beta form.
There is a catch, however. The “full Google Fi experience” is limited to devices which are “designed for Fi.” which includes the likes of Pixels and other devices sold in the Fi store. It means that they won’t be able to hop between T-Mobile, Sprint, and WiFi. It is a major limitation, but a start nonetheless. Google is yet to publish an official post about this change, but we can expect something in the next few days.
News Source: 9to5google