Scott, I don't think there is any out of box tool that you can use for this purpose. However, as each web session will record something like this in stdlog
04/29 07:59:00.42 MYSDM web:local 2528 SIGNIFICANT session.c 10883 Session 1198722824:0x1A6B41C8 login by analyst ServiceDesk (cnt:CA1234567891012221314151698765421); session count 96
so you could write a script reading messages in stdlog files and process and report real time
who logged in and how many sessions are on him/her.
I think you should investigate why you have over 1000 active sessions...for example, if the users
use IE and it is not configured properly, you could see multiple session for the same login.
Hope this helps a bit.
Thanks
Chi