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