A smart city is an urban area that uses different types of electronic data collection sensors to supply information used to manage assets.
When my ultrasound sensor stopped working, I decided to improvise by making an obstacle avoidance bot using IR sensors (cheaper too).
Guest alert system that keeps those nosy, unwanted guests/people away from your room, so that you can work without worrying.
Follows a black line.
How to Make a Line Follower and Android Application Control Robot using Arduino and MIT App Inventor