With the latest System Center Configuration Manager (SCCM) Current Branch update (build 1810), you can now request a client restart using the SCCM console.
To do so, open your SCCM console and reach out the Devices section from the Assets and Compliance workspace to select the device you want to restart
Right click on the device and choose Client Notification\Restart
If a user is currently logged on the client, he will get the restart notification in the systray as if a software/update deployment was requiring a restart. He will then be able to manually restart now or manage the delay (same as with software/update deployment)
If no user is currently logged on, the device will restart by itself immediately.
As for any client notification initiated by an SCCM administrator, you can monitor the status by accessing the Monitoring workspace and the Client Operations section