Best mechanism for change notification

Hello all,

I'm interested in writing a C++ client for postgres which needs the ability
to receive notification any time a value in the database, which the client
deems important, changes (this can theoretically be any value in any column
of the database). The conditions for this notification may change
frequently over the course of the programs execution. What mechanisms exist
in postgres to do this (I've briefly looked at triggers and Listen/Notify,
just want to make sure I'm not missing something)? Which method is the most
efficient, considering the constant need to update the trigger condition (or
is it best to delete the old trigger and create a new one each time)?

Thanks for your assistance,

Jason Donmoyer