UPDATE additional information and screenshots after Patch Tuesday
This has always been a nightmare for sysadmins, identifying devices with pending reboot.
Now with SCCM, it becomes easier. The latest update for SCCM Current Branch (build 1710) has a new column to use in the Console\Devices to identify such devices with pending reboot
To get this information, access the Assets and compliance workspace from the SCCM console and go to Overview\Devices. Then right click on the header of the device list and scroll down to get Pending Restart
With previous version you had to use Configuration Items and Configuration Baseline to identity them.
As a result, when a device is pending a restart, you know the reason of the pending restart
NOTE this attribute can not be used as filtering option neither to create a device collection (or at least I did not find the way to do)