In the joyful summer Chadalavada spent with Jayasree, his grandmother in 2018, the pair watched endless movies．Late one evening, Jayasree, who had recently been diagnosed（诊断）with Alzheimer's, got up in her nightdress and went to make tea at her home in India．After she returned to her bedroom, Chadalavada went into the kitchen to find that his grandmother had left the gas on!

Chadalavada decided to invent a wearable device to help people like his grandmother．Now aged 17, Chadalavada is ready to start making the Alpha Monitor．The device, which can be worn as an armband, sets off an alarm when the wearer with Alzheimer's starts to move and warns a caregiver if the patient falls or wanders off．

Most similar devices run on Wi-Fi or Bluetooth, so when a person moves out of their frequencies' limited range the connection is lost and with it the monitoring．But the Alpha Monitor can detect a person more than a mile away in cities and three miles in the countryside thanks to the long-range technology, known as LoRa, it uses．

Teaching himself with YouTube videos about robotics and electronics, Chadalavada has developed several prototypes（模型）．To understand the needs of people with Alzheimer's, he spent time in a day centre run by the Alzheimer's and Related Disorders Society of India．There, the co-founder told him that the device "had to be something light that can be worn on any part of the body"．She says: "Many patients don't like having to wear a watch and they take it off."

In March, when Chadalavada's school exams are over, he will put the finishing touches to the monitor, with the aim of getting the device ready for market by September．He is confident that it should be sold at an affordable price for most people．

Chadalavada hopes to study robotics at a university abroad．His aim is simple: "I want to create products to help people in India for the whole world."