AivarasFX

Plugin creates widget that displays simple horizontal login. 
If theme has registered sidebar on top, widget may be used to display Horizontal login for top of the page for webpage users.
Input boxes are aligned in horizontal way, not verticaly. For blog users there is no need to open wordpress login page to login.
If blog has WP-fb-autoconnect plugin installed, widget also displays Facebook connect button and allows users to connect using facebook credentials.

FX simple LoginLogout

Plugin displays simple horizontal login for top of the page. If WP-fb-autoconnect plugin installed users may connect using facebook credentials

codersantosh

AcmeIT

AddonsPress

Yam B Chhetri

This plugin limits login to one device at a time for a user. 
If the same user login from another device, that user won’t be allowed to log in. 
Admin can set up an ‘Already login message’ for that user.
If the user has been inactive for too long, then the user is automatically logged out and that user allows to log in again either from the same device or another device. 
Admin can set up ‘Auto Logout Duration’ for users.
It tracks the user’s activity like user status ( Active/Inactive ) and Last active time. 
Admin can view user status from WP Admin > Users > All users. From the “User Status” column, the user current status can be viewed.
Admin can set up only one device login limit plugin from WP Admin > Settings > Limit login
Note: This plugin is compatible with most of the membership plugins. 
If you find any issues, please use <a href="https://wordpress.org/support/plugin/only-one-device-login-limit" rel="ugc">support forum</a> to report.

Only one device login limit

Very useful plugin for security purposes



works like a charm

Limit login to one device at a time for a user. Configured options from the admin

FX simple LoginLogout vs Only one device login limit