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).
How to Make a Line Follower and Android Application Control Robot using Arduino and MIT App Inventor
DIY digital tachometer using IR Sensor and Arduino(No display, output shows on serial monitor).
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.
Be it Bird or your pet, automate their meal time according to proper routine. And receive an alert whenever you need to refill the meal.