Batch Site Manager, is that tool which is a hyperlink you will see after installing the toolkit to the MOSS box. This feature should be capable of doing all bulk operartions such as moving, locking and deleting site collections across content databases in a single web application as per MSDN.
Open Central Administration
clicking over the link will open up a new screen as follows and probably you will not see any site collections in the list. You will need to start the statistics aggregation timer job by clicking over "Click here" hyperlink which will populate all your site collections in this page
provide the details such as Target content database, Temporary file location and the schedule to start the job etc.
Yes, it can even send an email upon completion/Failure. So fire and forget. you can see a sample mail
I did not check this functionality with very huge site collection move activity, if any one carried out please let me know :)
for more information go here