It sounds like they are trying to radically rethink INS though, and if they can dramatically cut drift it would be a huge win. A drift-free INS is the holy grai

It sounds like they are trying to radically rethink INS though, and if they can dramatically cut drift it would be a huge win. A drift-free INS is the holy grail of location systems (IMO), and we don't necessarily require a 0-drift solution (just extremely low drift). Though you are right, a system depending on some entirely other phenomenon for location would be even more exciting.