Notifications on WordPress user logs in
Be notified when user has logged in on your website
It can be easily done by having the jetFlow.io plugin installed and using a tiny workflow. Install workflow from this page: http://jetflow.io/how-to/track-user-logins/. Once you have installed the jetFlow.io plugin add that workflow on the Tools admin page by using a download link to the workflow.
That automation scenario will send you an email every time a user logs in your website. You can setup sending notification via email, SMS or push notification to a mobile device or any browser. To be notified about login event for a specific user role like Administrator or Customer or a set of several roles just select them in the Restrictions box.
Another way: WordPress notifications made easy
The mobile way: Instant mobile and browser notifications