Radio 4 in Four - How accurate are wearable fitness devices? - ÃÛÑ¿´«Ã½ Sounds

Radio 4 in Four - How accurate are wearable fitness devices? - ÃÛÑ¿´«Ã½ Sounds
How accurate are wearable fitness devices?
Winifred Robinson finds there are surprising variations with different wearable gadgets.