In a nutshell, there is some code for doing delayed replication from inside the server, as an optional parameter to the CHANGE MASTER TO syntax. Maatkit has a script for doing this functionally externally, but an internal solution might be preferred.
If you have an urgent interest in this feature, in either MySQL 5.0 or MySQL 5.1, please contact me
for more details and current code status (link to relevant OurDelta
branch that has the work-in-progress patches).