In a car:
A speed sensor lets the system know if the car is travelling above or below the speed that has been set by the speed control.
Rotation sensors on the wheels let the braking system know if any of the wheels is about to lock up and skid. The ABS system then lets the brakes off a bit to prevent the wheel from skidding.
A tachometer lets the engine management system know when the speed of the motor is reaching its upper limit. When this happens power to the engine is automatically reduced.
A GPS system lets the driver know where the car is.
A light on the dashboard provides feedback about whether or not the seat belts are fastened.
Some cars have devices that provide feedback that prevents the car from being started if the driver is drunk.
There are often sensors that detect if the car is in gear, or if the clutch is depressed and they will not let the car start until it is safe.
A reversing camera is a feedback mechanism, and so are the sonars on the back bumper.
In a washing machine there is a sensor that provides feedback about the load being out of balance during the spin cycle, and automatically does an emergency stop, to prevent the machine from damaging itself.
In an aircraft:
Ground proximity radar lets the crew know if the ground is approaching too rapidly or if the plane is flying towards a mountain.
An altimeter lets the pilot know how far above sea level the plane is.
An attitude indicator shows the angle at which the wings are tilted.
An anemometer lets the pilot know how fast the plane is travelling through the air.
In an elevator a sensor provides feedback about the total weight that is in the elevator and will not let it start if the weight limit is exceeded.
It also detects if the elevator is falling too fast and automatically activates an emergency brake.
In a computer the Task Manger provides feedback about how many of the computer’s resources are being used by different pieces of software. This allows the user to stop some tasks and free up resources for other tasks.
In a ship a depth sounder provides feedback about how deep the water is under the ship, and allows the crew to avoid running aground.
In a toilet, a floating ball provides feedback about when the cistern has finished refilling and turns the tap off so it does not overflow.
In a microwave there is a sensor that provides feedback on whether the door is shut, and stops the machine from working until it is.
In your house there are sensors that detect if too much power is going to one part ot the house, and if so they automatically turn the power to that area off.
On a petrol pump there is a sensor that detects when the tank is full and automatically turns the pump off. It also detects when the correct amount of petrol has been pumped and automatically turns the pump off.
Air brakes on trucks automatically detect when the air pressure is lost and automatically put the brakes on.
In the robots you are building the sensors provide feedback about whether the robot has moved to the right or left of the line, and the robot uses the feedback to follow the line. We say the process is automatic, but it only happens because you write the program to make it work. The same is true with many other forms of feedback where computers are involved.