We've already seen jewelry that sends out an alert when its wearer is attacked – but they still have to push a button on it to make that happen. What if they can't reach their jewelry? Well, that's where the Smart Jewelry Bracelet comes in.

Currently in prototype form, the bracelet was created by Jayun Patel, a master's student and graduate research assistant in the University of Alabama at Birmingham's SECuRE and Trustworthy computing Lab (SECRETLab). It incorporates an Adafruit Circuit Playground, which is a microcontroller equipped with a gyroscope, accelerometer, temperature and pressure sensors, GPS and microphones.

"The sensors allow the bracelet to collect user activity and vital signs continuously," says Patel. "It can also determine the orientation of the user, for example, whether they are standing or lying down. A machine learning algorithm detects and differentiates the user's regular movement and unexpected and sudden movements that can be indicative of an assault."

When such unexpected movements are detected, the bracelet emits a loud beeping sound and begins flashing its red LEDs, in order to alert passers-by. It also connects to the wearer's smartphone via Bluetooth, then sends a message to the police and to pre-selected people on the user's contacts list – that message includes the user's present GPS coordinates.

The prototype cost just US$40 to make, and could likely be mass-produced for much less. Patel is now looking at adapting the technology to other wearable items, such as earrings or shoes, that could send an alert when elderly or disabled wearers fall down.