Heads Up Notifications topic

Does anyone know how to change what gets displayed as Heads Up in 5.0? I have the settings in Sounds and Notifications > Interruptions setup like this:

When Notifications arrive: Always Interrupt
Events and Reminders is ON
Messages is ON
Calls/Messages from: Anyone
Downtime: NONE

The only apps that seem to do heads up is Facebook/Facebook Messenger. I'd like other apps to be able to show heads up when I'm in a full screen app. Is there any way to do this, or at least have it show the status bar to see the notification icon for a second or two when I'm in the full screen app, to decide if I want to check the other app?

Heads up topic

Do we not have heads up on the stock? Unless I am dumb and can not see it.