Google's Project Fi, which was recently introduced by Google and officially support only Nexus 6 Android smartphone. But now, Nexus 6 is not the only device which is compatible with Project Fi and make use of all of its features. Moto X Pure Edition also able to work fine with Google's Project Fi.
As tested by Droid Life, new Moto X Pure Edition successfully activated on Google's MVNO network using an unactivated Project Fi SIM card from Google. Moto X recognize the project Fi SIM card and assign a phone number after activation. Then the device is able to use LTE data, voice calling, web browsing without any issue.
Project Fi, that is programmed to provide better network connection by using best available network between Wi-Fi and 4G LTE networks, and uses cellular network of two of the leading carriers in the US, Sprint and T-Mobile. But this Test by Droid Life couldn't confirm whether the voice call connected with WiFi, can actually utilize WiFi calling on Fi, and whether it change cellular network among both partner during the voice call.
But some source claims that the used Moto X device with Project Fi, may use only one cellular network for ever and never be able to switch to another cellular network. Yet, there is no official announcement from Google about supporting of Project Fi SIM card on Moto X device, and Google's Project Fi official website showing only Nexus 6 as compatible device that works on Project Fi SIM card.