Yeah I'm not thinking so much stopping at lights and in traffic for this application, but something like if the parking brake is engaged and 15-30 seconds pass, then engine turns off. As the trucker in this thread noted, sometimes they'll hop out expecting a quick stop and it balloons into 15 minutes of idle waiting on other people. Then there's the drivers who will let the truck idle while getting loaded/unloaded just for climate controls.... And thinking at scale saving even just a gallon, multiplied across a whole fleet, could be a big impact.

Of course there's more thought to put in for secondary systems, but just strikes me as something that should be considered.