we have a batch process to export all ps_mstr records to a file every day. Next day when the batch runs again it reads the file into a temp table an then matches ps_mstr against the temp table looking for changes, and also matches the temp table against ps_mstr looking for changes. List of changed records sent to users.

This year we implemented ProStar's TailorPro audit tool to watch some fields in ps_mstr (and pt_mstr). 

You can also use the simulation cost functionality to compare the with the standard cost. This will give you anser which BOMs were updated.