The number one item from the OSCON session by Robert Lefkowitz (r0ml) on "The Missing Open Source Projects" is...
I would look to the Erlang framework for this. Simple, distributed, robust, persistent, monitored, and integrated. I'd guess the Erlang OLTP is well above 80 percent of what is needed for an industrial strength distributed CRON.
More systems should be emulating the Erlang framework for distributed systems development. (Assuming programmers by and large are not going to adopt the Erlang language per se.)