I'm looking to replace my iOS app which relies heavily on the UIWebView and the JS-Bridge component with the newer WKWebView element, to take advantage of the improvements in JavaScript rendering speeds and so forth. I've seen some work on GitHub by @Skall for Xamarin.Forms, however I have not been successful in utilizing the code in working in a Unified iOS project (sans Forms).
I've found some resources that I feel like is getting me closer to my objective, but I'm still having trouble getting past rendering a simple HTML page in the WKWebView and getting any JavaScript embedded within it to successfully call.
https://forums.xamarin.com/discussion/41777/wkwebview-caching-not-working
Objective-C option (proofing it can be done in native)
http://www.joshuakehn.com/2014/10/29/using-javascript-with-wkwebview-in-ios-8.html
For what it's worth, I'm only targeting iOS9 and newer versions. I know with iOS8, there were some issues/bugs that went along with WKWebView.