Low-tech 2.0 version: Two tennis balls on the rope, neon-colored. A green one at the end of the rope and an orange one 3ft higher. When going up the hill head for the orange ball, when leveing off in the garage stop when the green ball touches the windshield.
The ball in our case is mounted such that it lines up with the driver and steering wheel.
We have a similar problem but not with the garage. My wife is also petite and no matter how things are adjusted in my car she cannot reach the pedals.