Well from my perspective it's totally worth mentioning Arduino, not because it is something too technical but because of the various works, it can perform. Before starting I just want to give some technical information about it, so that one who does not know even a bit about should not feel like an alien here. 

Arduino is a means for sensing the information from the outer world, giving it to process, and then making your computer do more from it. It's IDE (Integrated Development Environment) allows users to write software for the board, thanks to its open-source physical computing platform which is mounted on a simple microcontroller board. As stated earlier, Arduino takes input from the physical world through a variety of sensors attached to it, processes the information according to the written program, and controls the actuators for motion or lights to give the desired output. Arduino projects can be used to take inputs only from the physical world, or they can communicate with software on your computer.

Some examples where one uses Arduino frequently are as below -

 Medical Instrument, Emergency Light for Railways, Parking Lot Counter, Weighing Machines, and Traffic Light Count Down Timer.

Apart from these, there are a lot of places where some board equivalent to Arduino is being used (Maybe someone is really using Arduino there) are,

 Washing Machine, Microwave Oven, Window Aircon controller, Security Systems, CCTV Switchers, For Automatic Opening Dustbin with Ultrasonic Sensor, For making Drones, For making Line follower Robot, For usage in the Internet of Things (IoT), For making security devices for the home, To measure Temperature And a very long list .......

Something more which you never asked but may be useful.

However, do not that Arduino board usually have just a microcontroller and you need to add a lot of extra peripherals to do even a simple basic job. Arduino by Arduino is first or unique. There is plenty of other microcontrollers more powerful and cheaper.

While searching about various applications of Arduino board, I was surprised to see that even a high-profile museum was using it for its security. One can imagine the versatility of this small board if it is being used for security. I hope that one should ponder upon my article and at least once try to make use of the Arduino board. It will become a productive hobby. Thank You For Reading.