Google is apparently working on better integrating Android with iOS and macOS. Quick Share is to be used for this.

This solution is said to be baked into Color OS 15 and can wirelessly transfer files such as photos, videos, documents, etc. However, you may need to install an app on iOS.

Install or update Office Mobile, Word, Excel or PowerPoint to version 16.0.14931 or higher on Android or version 2.58.207 or higher on iOS ...

If you've switched from iOS to Android and you need your SMS messages transferred, your best bet is iSMS2Droid. Jack Wallen shows you how to port your messages using the app and an iTunes backup.

Think about it: Apple could as well introduce “sideloading” for applications in iOS 5. Android users, in fact, have been able to install apps from unknown sources (sideload, indeed) for a long time ...