Looking at how the OS relies of some of the APIs in Android 4.3+, it is pretty much clear that until and unless Apple provides similar APIs in iOS, it will not be possible to use an Android Wear running smartwatch with an iPhone.
However, it looks like developer MohammadAG – popular for some of his Xposed modules — has managed to get Android Wear to work with an iPhone. A short video posted by him on YouTube shows a notification for an incoming message on his iPhone 6 popping up on his Moto 360.
The developer has not yet provided any more details on how he managed to get Android Wear to work with an iPhone,
but it is evident from the video that the method requires a jailbroken iPhone to work.
While this news will not send iPhone owners flocking to buy an Android Wear powered smartwatch, I presume it will still come in handy for some people out there.
Update: As informed by the developer in the comments, a jailbroken iPhone is not required. Additionally, he has also revealed that he made use of Apple Notification Center Service (ANSC) APIs to get his Moto 360 to work with an iPhone. This is similar to how Pebble is able to get its watch to work with the iPhone.