Question about remote monitoring

I have read about passive checks…
is THIS possible?
Have remove windows pc’s running the NSClient++ and sending data to my Nagios server in our data center?
I have nagios running and monitoring our and our customers servers. However, we would like to expand it and use it on the customers site and avoid having to use a tunnel to monitor.

Is what I am asking easy to do without placing another nagios box on site?

My company is looking at doing the same thing. NSCA will work for this and post checks back to your server. The only issue we ran into was trying to do active and passive checks on the same server. Our new plan is to have a nagios server running checks on each customers site and one for our local stuff all reporting to one that just accepts passive checks and doesn’t do anything else. There may be a better way to do this with version 3 but we’re not touching it till it’s stable.