This is the 'technology' that Alfa use .... courtesy of Wikipedia:
In layman’s terms, the hill holder function works by using two sensors, in concert with the brake system on the vehicle. The first sensor measures the forward facing incline (nose higher than tail) of the vehicle, while the second is a disengaging mechanism.
When a driver stops their vehicle on an incline where the nose of the car is sufficiently higher than the rear of the car, the system is engaged when the driver's foot is depressing the brake pedal, and then the clutch pedal is fully depressed. Once set, the driver must keep the clutch pedal fully depressed, however, they may remove his or her foot from the brake pedal. To disengage the system and move the car forward, the driver selects first gear, feathers (applies) the gas pedal, and slowly releases the clutch pedal, which, at a point in its travel, releases the braking system allowing the car to proceed.
