The problem is the certification and cost.
Is that true considering the total cost of a single a/c. If it was designed in at manufacture and amortised over a world fleet lifetime, would it be that expensive. I wonder if the same thing was said about FDR's & CVR's. There are already outside viewing cameras, so the technology is there. F1 has much expertise, although at different speed & temperature. However, it would not be a go/no-go item, probably.