AFAIK, there's nothing standard in postgresql to support this directly.
You could add a trigger in the to update a timestamp in a separate "flag" table when changes are made.
Is the remote server running on Windows or Linux? If it's Windows, and you have install priviledges, you could write/install a little monitor app that polls the table periodically (every second or two) to check this "flag" table. If the flag is set, signal your client app using winsock.
Note. You might also consider this: If you set up a distinct, separate tablespace for your target table (and ONLY the table) then changes to the table will result in the tablespace data file timestamp being updated... You might be able to monitor a file remotely...
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