New OnePlus Switch app allows users to migrate data to a new OnePlus smartphone
For the time being, the application supports the transfer of Contacts, Messages, Call Logs, Calendar, Photos, Video, Audio and Applications (without data). However, OnePlus confirmed that it will soon provide “Applications with data” transfers as well.
OnePlus Switch does not support iOS devices, so if you plan on dumping your iPhone for a OnePlus smartphone, you won't be able to transfer your data using this application.
source: Google Play Store via AndroidCommunity
Things that are NOT allowed: