I've been using LMI Rescue for 10 or so years. I've heard of Hamachi before, but only used it once or twice many years ago to emulate a LAN for multiplayer games.
I recently started a project building a robot that has a Raspberry Pi onboard. It uses an LTE cellular link, and my ISP wants $500 to open ports, most of my VPN solutions weren't going to work.
I spent a lot of time setting up a reverse SSH tunnel. The problem with that is it would be very hard to add clients. It would also require a public facing high availability SSH server.
After a lot of research I ended up thinking what about, wait, what was the name of it? Oh yeah Hamachi.
Sure enough there was an ARM installer, and it took 2 minutes to get it running on Raspberian. On the Pi, I set it up as a gateway. I was pleasantly suprised that it is IPSEC. I could add people instantly right through the LMI site, and then manage them as well. I sent an email to my phone, and to my PC. Took all of 10 minutes.
I will end up purchasing this, even though I don't need more than 5 users. It's the perfect solution for a Raspbery Pi over a cellular, 3G/4G LTE network.