> It also would be a harder boundary to draw than you might think

As an example my 2010 Toyota has an automatic parking system[0], which connects the backup camera, infotainment system (for display and input), steering control and parking sensors.

[0] Which to be honest is basically pointless. It works, but takes a lot longer to setup and use than just parking yourself.

exactly.

or remote start, remote diagnostics, tire pressure monitoring systems, maintenance reminders, electronically controlled suspensions, many traction control systems, etc.

Not arguing those features should/need to exist but they are heavily dependent on UI/control system data exchange.

You clearly haven't owned a boat to understand what "costs money" means. An expense that would have your average automobile owner up in arms about would be pocket change for even the smallest of boat system systems.

And for the majority of boats out there this is a total non-issue as they're not even going to come close to having any of this integrated in any usefully hackable way.

So unless you're talking about the 80'+ class of boats or megayachts things are still based on circa 1990's tech, at best. Even the big boats don't integrate all that much.