Just a few comments regarding the Ewon Cosy VPN router and its integration with Unistream controllers.
I have used the Cosy to remotely connect to a Unistream 10.4" HMI via VNC through internet and it works great.
I also used the NAT 1:1 function, so that the user won't need to use internet when connected in the same LAN.
Connection is 100% reliable and response is relatively quick, there is a bit of lag but it is fairly acceptable.
It takes approx. 15 min to set it up and get it working, only very basic networking knowledge needed.
Connection is achieved via Ewon's M2WEB cloud service and requires to have a valid TALK2M account.
Unit price for a COSY 131 is quite high (490 Euro), but in my opinion it is worth as connection security is number 1 priority.