Data exchange between 2 remote postgresql databases

Question

As per subject I'm looking into a reliable way to synchronize 2 tables that have a same structure between two remote postgresql databases.

I was thinking about dblink but an not really sure as in the places where these db's are connectivity is a big issue and very unreliable and this would force me to expose my databases to the internet which is an idea I'm not comfortable with.

Another option would be to write myself a daemon implementing integrity checks but before proceeding I'd like to know if anyone has undergone a similar challenge and what solutions have been undertaken.