Boy, this sounds like a shop I used to work at. Do I know you from somewhere? ;-)

As I recall, HP-UX doesn't have anything like a /proc file system, so you're limited to tools like ps. What I did (and you're right, it's very sloppy) was to write a script that read the output from ps, saved the TIME column against each PID in a hash, slept, then did it again, and compared the time for each matching PID. If it was greater than a threshold, it printed a message (in your case, you would send an email).

I'm reconstructing this from memory, so you'll have to make this work for real, but the code basically looks like this:

my (%current, %previous);
while (1)
{
   open PS, "ps -ef |" or die "Can't run ps: $!\n";
   while (<PS>)
   {
        # you need to do this with the correct column
        # widths; something like split won't work,
        # and a regex would be way too complicated.
        my ($pid, $time) = unpack '...';
        $current{$pid} = $time;
        if (exists $previous($pid})
        {
            # difference sub is an exercise for the reader....
            if (difference($current{$pid}, $previous{$pid}
                >= $threshold)
            {
                 warn "$pid is a piggy\n";
            }
        }
    }
    close PS;
    %previous = %current;
    sleep 3600;
}
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Sorry I couldn't be more specific. HTH anyway.