It's something we have discussed from time to time. The challenge is that it would require deploying code to all of your desktops. That's a management challenge. How many of you would do that?
Here is a solution you might want to give a try.
If you have APM, you could run a VBscript that remotely run the "netsh diag ping" commands to check e.g. if you can ping the gateway/DNS servers and return the response time to APM with a Up/Down status depending your network thresholds. Concerning the DNS, this does not really try to resolve a domain names :\ ...but scripting can solve that.
You can as well connect to websites using the "netsh diag connect iphost thwack.com 80" command.
IPHost = thwack.com
Port = 80
Server appears to be running on port(s) 
Once your scripts are working well, integrate them in APM with the Windows Script Monitors.
If you are not familiar with VB scripting I agree that it might take a while before to have monitors ready.
Another alternative for the Ping monitor would be to use the Win32_PingStatus WMI class as part of a WMI Performance Counter Monitor: Re: wmi ping, what is wrong here.
Well we wouldnt really want to install it on all our desktops only 1 or two devices per switch or vlan whichever is supportable. This would allow us to see if the user vlan is showing issues or not. It may be that you only want to install it on a handful of probe devices around the network to see how there responses differ.
You might be thinking why doesnt he just use Cisco IP SLA for this. The point is to ensure that the probe mimicks or is the host as much as possible rather than just the Distribution router(or where ever your IP SLA.
In addition to the additional perspective you will gain from outlying segments of the network you may have the option of doing the following.
Set up a monitor for your main web site
Set up a number of hosts which represent the fastest and slowest parts of your network to poll the web site , and report to orion. You can then aggregate the results and provide an accurate measurement of KPI;s and SLA's from the clients perspective in general.
I presume from the limited interest in this topic that I am on my own on this one:-)