Nice speech, but creating a new side channel on the PSTN is really hard to do. It requires standardization and the coordination of telcos, operators, device man

Nice speech, but creating a new side channel on the PSTN is really hard to do. It requires standardization and the coordination of telcos, operators, device manufacturers, world-wide, many of which only have partially digital networks. (Think about how hard it would be to add a new field to TCP.)