That seems like a no-brainer feature for any “firewall” plugin.
For example, WP Simple Firewall shows in their documentation that they have a really nice reporting of logged in users. I’m beginning to realize that in the fight against online criminals, information is power. A good firewall or other type of security plugin should overwhelm us with information, perhaps with options to turn such information on and off as needed.
From WP Simple Firewall documentation: On the ‘User Management’ section of the plugin, below the options, you can view tables of failed logins, and currently active sessions.
It outlines:
the time they logged into this session
their last activity time
the last page they accessed
the IP address from which they’re accessing the site (which links to an IP Whois)
and how many attempts it took to login (normally 1)