Most (all?) of these integrated systems use the stability control yaw sensors to detect the butt getting squirrelly. If the system does not detect a connected trailer, it will work as normal to control stability. If a trailer is detected, the system may employ a "sway control" type of algorithm, which may include applying some trailer braking. This is the sort of thing an aftermarket controller can never do, having only 1 sensor in 1 location.
As far as the braking "force" at rest? When at rest, none of the vehicles motion sensors will be detecting any motion. So of course, the only way to increase voltage is to respond to brakeline pressure (not pedal force). Aftermarket controllers simply apply 25% (50%? I can't remember) of set voltage if no motion is detected after 2-3 seconds, if the brakes are held. But having variable voltage, based on pressure is great.
But some are saying that these integrated controllers are not inertia-based. That's very limited thinking. The integrated controllers are certainly taking data from the stability control sensors, which are inertia-based accelerometers. It's also pressure data, speed data, wheel-speed sensor data etc. To say it's not inertia-based is not correct. I'm sure it's using everything that the ABS/TC/SC systems have to offer.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller