A smart city is an urban area that uses different types of electronic data collection sensors to supply information used to manage assets.
Guest alert system that keeps those nosy, unwanted guests/people away from your room, so that you can work without worrying.
Building cleaner, greener and smarter cities with IOTA.
Using a IR proximity sensor and microcontroller to find the local values of 'g' and will plot a real time damping curve.
When my ultrasound sensor stopped working, I decided to improvise by making an obstacle avoidance bot using IR sensors (cheaper too).
An empty place indicator or monitor for car parking.