That depends on if you want to pay, or if you want it for free.
Free would be logmein, it's a great way , one of , if not the best desktop viewing clients out there. Awesome.
Another would be Team Viewer , another free one, but I don't believe that it's as secure, maybe it is.
edit~~~~~~~~~~ actually, I read what you wanted again, and these are not it, you should set up a VPN.