Sony Mobile’s latest update (38.3.A.0.94) to the Xperia X Concept includes a new feature called “ambient display”, which will wake the screen when you receive a notification (similar to the iPhone). The feature can be turned on and off in the display settings.
The camera viewfinder has also been updated to include a fixed level of brightness that is independent of your current screen brightness. The idea behind this is that it should better match the actual photo taken.
There are also a number of bug fixes including Bluetooth audio loss due to OK Google, a fix for tinted display colours even if Night Light was not activated, and a fix for the notification LED not lighting on a missed call. The update is now rolling to all those on the Experimental track.
Thanks Josef and najodleglejszy!