OK, here's an idea. You write a set of stored procs that let you do
something like:
insert into batch_jobs ('..... I'm not sure what we'd put here...)
then, postgresql has a crontab entry that uses something like redhats
runparts script to run the SQL commands it finds in the table.
I.e. the jobs could be scheduled by something as simple as a query, and
removed as well. Just need a postgresql cron that runs every 5 minutes or
whatever resolution you need.