People who use wearable gadgets to monitor their health or activity can be tracked with only $70 (£40) of hardware, research suggests.
The work, carried out by security firm Symantec, used a Raspberry Pi computer to grab data broadcast by the gadgets.
The snooping Pi was taken to parks and sporting events where it was able to pick out individuals in the crowds.
Symantec said makers of wearables need to do a better job of protecting privacy and handling data they gather.
Read more on BBC.
Related: Symantec: How safe is your quantified self? Tracking, monitoring, and wearable tech