iOS seems to have a fully functioning HTML5 browser. (:

There's also no iMessage on Android.

Also, Fi support for iPhones is listed as beta, and I don't think there's ever been full support for iPhones on Fi.

Finally, if Apple were to launch a Fi-like offering, I don't think anyone would expect even marginal support for Android devices. This is not to say that you couldn't get service working on Android, just that there would be literally 0 support from Apple for such a use case.