Hi @jsnider, apologies for the delay whilst I tried to confirm the situation with the calibration blob.
Whilst certainly the calibration blob object is of little use outside of the Tobii Pro SDK (as you indicated) at the very least it should never the less allow you track that the user has indeed changed. However, the calibration blob would change and the user remain the same if the user in question chose to recalibrate manually, so something to bear in mind.