Teamviewer

 An excellent tool. Mainly used for customer support, but great to manage any rig. Using this private, and for business, for years. The great thing is that it just works, and always has, without any hassle. Install and it works.
Would give this a 5 Star, but it has one massive drawback. It's unlimited to use for personal license. As soon as commercially used (mining indeed is considered as commercially used), you need a business license. And the software starts to limit your sessions to 30s or less when it thinks it has detected that you use it these ways. It's pretty annoying... and a lot of people get hit by this for no reason and false reasons.
All of a sudden I could not access my machines anymore than 15s and was not able to manage them and had to go with a paid license.... awe full way to force customers into the service.

So I'm ok with paying for software that is great, but the commercial license is extremely expensive, and suddenly extremely limits to how many machines you can access. That's pretty annoying and a real bad pricing policy, as the free personal has no limitations at all!