Vehicle must be in neutral with the brake engaged. When the key is removed, it will run a 2 second test in which the engine will run. If the test fails, it will not start that cycle. The battery will still be monitored and the audible alert will still activate but active charging will not engage until the vehicle is started with the key and it passes the next test. Operator must put the vehicle into test mode before shutting down (push button). No matter what, the battery is being monitored and can even be configured to disconnect the accessories (like a fridge) that are causing a drain below threshold. So even if the operator forgets to activate the test, he is still protected from being stranded.
People with auto trans do not have to do anything special... it's the nature of the beast.
Since we're all responsible rig owners who pass safety, I am sure every has a good parking brake.