Security analysts at Symantec have found that they were able to track users who engaged in the ‘quantified self’, or tracked their lives using fitness or health apps, by using a $75 product dubbed the ‘Blueberry Pi’.

The security bods mashed together a Raspberry Pi (price: $35), a battery pack, a Bluetooth USB dongle and a 4GB SD card to create a device which could track these apps and can be built by “anybody with basic IT skills.”

These portable Bluetooth scanners were...