On Subarus it requires a small device mounted on the fender with a brake line running through it; I read that Subaru copied it from Studebaker. On the C-max, I think one of the electric motors is holding the car in place, not the actual brakes, and it just requires some lines of code...
Hill Start uses the brakes as described in the Service Manual. Every car I've owned for quite some time has had this feature. The ABS uses the stability sensor messages from the Restraints Contol Module. When the ABS determines the vehicle is on about a 3% grade or more, it enables the Hill Start function. If the ABS determines there is insufficient torque once the brake is released and the accelerator pedal is pressed to move the vehicle, it will continue to hold the vehicle in place beyond the normal hold time. The Hill Start function works in both forward (D) or reverse ® if backing up a hill.
From the Owner's Manual:
The system makes it easier to pull away
when your vehicle is on a slope without the
need to use the parking brake.
When the system is active, your vehicle will
remain stationary on the slope for two to
three seconds after you release the brake
pedal. This allows you time to move your
foot from the brake to the accelerator
pedal. The brakes are released
automatically once the engine has
developed sufficient drive to prevent your
vehicle from rolling down the slope. This
is an advantage when pulling away on a
slope, (for example from a car park ramp,
traffic lights or when reversing uphill into
a parking space).
The system will activate automatically on
any slope that will cause significant vehicle
Using Hill Start Assist
1. Press the brake pedal to bring your
vehicle to a complete standstill. Keep
the brake pedal pressed.
2. If the sensors detect that your vehicle
is on a slope, the system will activate
3. When you remove your foot from the
brake pedal, your vehicle will remain
on the slope without rolling away for
about two or three seconds. This hold
time will automatically be extended if
you are in the process of driving off.
4. Drive off in the normal manner. The
brakes will release automatically.