The Current "Online Status" for both iOS and Android users:
When two people are on a 1-1 chat and someone puts their app in the background, the other person would see their status change to "Away."
However, If you receive a missed call, the statuses behave differently on iOS and Android. If you are on iOS, your status will change to "Last seen now.” If you are an Android user, it changes to "Away" as expected.
For Android users, if you play a radio station or MP3 and put the app in the background, your status will show as "Online" to other people.