Amusingly enough most of them aren't - OBD access to interesting features (as opposed to a very limited standard set) usually costs a LOT of money. $10K one-off

Amusingly enough most of them aren't - OBD access to interesting features (as opposed to a very limited standard set) usually costs a LOT of money. $10K one-off charge plus an update subscription for example. OBD-II has essentially failed by allowing so-called "extended" PIDs - which all manufacturers define in their own specific ways. See the Torque forum for endless threads of people wanting extended PIDs for specific models to use with the Torque OBD app. I suspect this is one reason why good OBD scan tools cost a lot more than the parts cost of an ELM chipset and a few sockets - a trivial adapter costs £20, but a Bavarian Tech scan tool for BMW costs £200, presumably to recoup the costs of buying access to the extended PIDs.