My question is fairly straight forward - can iOS create a Wi-Fi Direct group that can be joined by non-iOS devices?
The only information I can find relating to iOS direct peer connectivity is https://developer.apple.com/library/prerelease/ios/documentation/MultipeerConnectivity/Reference/MultipeerConnectivityFramework/index.html
More specifically, "The Multipeer Connectivity framework provides support for discovering services provided by nearby iOS devices..."
Based on this I would say no, but technically speaking, there should be no limitation for Wi-Fi Direct as it is an open standard, and apps like AirDrop already use it.