Android Wear has officially launched on iOS devices as of today. Through the Android Wear app currently in the App Store, iOS users are no longer limited to the Apple Watch or Pebble for wearables. Users of the iPhone 5, 5C, 5S, 6, or 6 Plus with iOS 8.2 or newer are compatible with Android Wear.
Officially, Google is supporting this year's round of Android Wear devices: the LG Watch Urbane, an unnamed watch from Huawei used in the press release, and future products from Asus and Motorola. This writer was able to get the original Moto 360 to run on an iPhone 5S without issue, so the issue appears to be a matter of out of the box support; only the newest version of Android Wear is supported, but existing devices will not have them out of the box, and they cannot be updated other than through the host device. Others have reported it working with the other devices—LG G Watch, LG G Watch R, Samsung Gear Live, Asus ZenWatch, and Sony Smartwatch.
In addition to getting notifications on the watch, Google has also integrated Google Fit for fitness tracking and Google Now functions, such as voice search and automated cards for weather, travel, package shipment, and others. However, it will only be pulling this information from Google sources—so that means no Siri, no Healthkit, no Apple Maps, or other aspects of the Apple ecosystem.
This is a very good thing for all users. While a very good device, the Apple Watch is priced significantly higher than its Android Wear counterparts. Android Wear devices also come in a much larger variety of sizes, and can also provide a usable wearable for those that prefer round watches as opposed to the Apple Watch's rectangular body.