bluearc
bluearc has had something similar for a while, no direct experience with this, though we used to be a bluearc customer -
http://www.bluearc.com/html/products/migrator.shtml
Application-agnostic, BlueArc Data Migrator also allows automatic data movement between tiers in a way that is completely transparent to related applications or end users. In fact, they will be hard-pressed to know the data no longer resides in its original location.