Monitoring multiple remote networks



I am looking into deploying a monitoring solution which will contain multiple remote sites that are not currently or going to be connected via ipsec tunnels. I have setup groundwork and so far so good. My question is what are the best methods on getting these sites connected? I have read up about utilising nsclient++ with tntmonitoring to form an ssh tunnel back to the nagios server but im unsure of what is required for me to do that. Im really stuck on the comms side of things.

Any advice will be appreciated.