Just a quick one, there might be better ways – but this is quite easy to do.
1. Open perfmon (run -> perfmon or Administrative Tools -> Performance monitor)
2. Create a new counter set (icon on the top left)
3. Add a new Counter (the button with the + sign)
4. Fill-in your front-end server in "Select counters from computer"
5. Select "Web service" as the performance object
6. Select the counter "Current Connections" and choose the websites you want to monitor
Repeat step 4 to 6 for every front-end.
koning53