READ UNCOMMITTED in postgres

Hi,
With the current READ UNCOMMITTED discussion happening on pgsql-hackers
[1], It did raise a question/use-case I recently encountered and could not
find a satisfactory solution for. If someone is attempting to poll for new
records on a high insert volume table that has a monotonically increasing
id, what is the best way to do it? As is, with a nave implementation, rows
are not guaranteed to appear in monotonic order; so if you were to keep a
$MAX_ID, and SELECT WHERE p_id > $MAX_ID, you would hit gaps. Is there a
clean way to do this? I've seen READ UNCOMMITTED used for this with DB2.

Thanks
Matt

[1]
https://www.postgresql.org/message-id/CANP8%2Bj%2BmgWfcX9cTPsk7t%2B1kQCxgyGqHTR5R7suht7mCm_x_hA%40mail.gmail.com