This approach is based on the article http://jaspan.com/improved_persistent_login_cookie_best_practice with some minor modifications [3]. To use the this approach with namespace configuration, you would supply a datasource reference:
<http>
...
<remember-me data-source-ref="someDataSource"/>
</http>
The database should contain a persistent_logins table, created using the following SQL (or equivalent):
create table persistent_logins (username varchar(64) not null, series varchar(64) primary key, token varchar(64) not null, last_used timestamp not null)
[3] Essentially, the username is not included in the cookie, to prevent exposing a valid login name unecessarily. There is a discussion on this in the comments section of this article.