The Moto X4 is an okay phone, but it's tough to recommend at $400. However, Google's Project Fi just started selling the phone for much less. You can get the Moto X4 for a mere $249 on Fi right now, making this a smoking hot deal.
The Moto X4 sold on Project Fi is the Android One variant, which has a few software differences compared to the retail version sold by Motorola. There's no Alexa integration or multi-device Bluetooth streaming. It got its Oreo update a little faster, though, so maybe it's worth the tradeoff. You also get a water-resistant chassis, a 1080p LCD, and a Snapdragon 630 SoC. The dual 12MP camera setup is better than devices you can get for $250, too.
— Google Fi (@googlefi) February 2, 2018
This discount is applied during Fi checkout automatically. However, you need to activate the phone on Fi within 30 days. If you don't, Google will charge you the full price of the phone. There's no minimum length of service needed to qualify for the discount. You can sign up for the lowest Fi plan and cancel it immediately. The Android One Moto X4 is a universal unlocked phone, so it'll work on any carrier.