Hi I have an iPhone what should I buy a Apple Watch 
or a finow x5?
In the FAQ page by @Lokifish_Marz are reported the possible interactions between D5/X5 and the iPhone.
Based on that list, you can choose what is right for you.
Here, we don’t even know what an Apple Watch is 
Is an Apple Watch a new type? I is juicy? and how long does it run on 1 apple?