Is anyone doing single device tracking?

It turns out that that this question has two answers.

Single device tracking can mean a unique identifier burned into a device's memory at the wafer level. This interpretation of single device tracking has been in place for many years especially for CPUs and memories.

However, single device tracking for multi-chip packages in which the unique identifier marked on the package can be used to trace all the devices within the package back through the assembly process to the wafer (Id + XY) is new. To achieve this requires coherent data representation across multiple process steps such that that defined in the SEMI E142 standard. The first such system based on SEMI E142 went live in 2009. Several more are in various stages of development.