Welcome to the Community!
At this time, we don't offer Smart Watches, so we don't accept them as trade-in devices either.
That said, you can still buy any Apple Watch, both the cellular and non-cellular version and bring it to Fido.
You’ll be able to pair with a compatible iPhone using Bluetooth or Wi-Fi, but not our LTE network. You can check the most recent compatibility on apple.com/watch.
Connecting it through Bluetooth or Wi-Fi allows you to enjoy its most popular functionalities (e.g. GPS, heart rate sensor, health apps, etc.).
Apart from the cellular capabilities, both versions have almost the exact same features.
Hope this helps!