pgplsql and notifications

Hi all,

I would like to implement a function in plpgsql (or sql if it is possible)
that can say me if I had some notification of some listened table. I mean
something like this:

create procedure do_i_have_notifications(text) returns boolean as '
...
' language (plpg)sql;

(or:

create procedure received_notifications() returns setof text as '
...
' langugae (plpg)sql;
)

Is there a way to do this?

Thanks,

Attila Ken�z