You can directly connect 2 openSPOTs together by setting one of the devices as a SharkRF IP Connector Protocol Server, and the other as a Client. If the IP address of the site of the server is dynamic then you can use a dynamic DNS service provider to point a hostname to the dynamically changing server IP address, and enter that hostname to the client to connect.
If you want to connect more than 2 openSPOTs together, then you can use the SharkRF IP Connector Protocol server software at https://github.com/sharkrf/srf-ip-conn-srv