What type of OS is installed on Server A and Server B? Actually only Server A is important in this case I think.
There might be a built-in monitor to achieve this, but I'd have gone with a script monitor. If it's a Linux/ Unix machine, you could create a shell script looking roughly as follows:
ping -c 4 127.0.0.1 | tail -n 2 (just replace 127.0.0.1 with the IP or FQDN of Server B)
It should produce something like this:
4 packets transmitted, 4 received, 0% packet loss, time 3002ms rtt min/avg/max/mdev = 0.035/0.067/0.105/0.032 ms
Place the script in the user Sitescope logs in as' home directory under subdirectory "scripts". If your Sitescope logs in as user "sitescope" for instance, the full path will then likely be "/home/sitescope/scripts" (on Server A, not on your Sitescope machine itself).
You can now configure a script monitor and have the regex set as follows:
This will give you counters on the % packet loss (0 in this example), minimum round trip time (0.035), average round trip time (0.067), maximum round trip time (0.105) and whatever "mdev" signifies (0.032).
You can add your own custom labels for each, then set your thresholds accordingly.
If Server A is a Windows machine then things will look slightly different, but the concept should be roughly the same. Hopefully this gives you the idea, but if you want to go with the script solution and get stuck, let us know.