From ezlinuxadmin.com
Have root logins emailed to you
1. Login to your server and su to root, unless you logged in as root already.
2. cd /root (unless your default login folder is already root)
3. pico .bashrc (or use your favorite editor)
4. Scroll to the end of the file then add the following:
echo ‘ALERT – Root Shell Access (YourserverName) on:’ `date` `who` | mail -s “Alert: Root Access from `who | cut -d”(” -f2 | cut -d”)” -f1`” you@yourdomain.com
Replace YourServerName with the handle for your actual server for example dwhs4 @ dwhs.net
Replace you @ yourdomain.com with your actual email address for example support @ dwhs.net
5. Crtl + X then Y
Now logout of SSH, close the connection and log back in! You should receive an email address of the root login alert a few minutes afterwards.