You may use the technique where basically you need just dump out all the data from the whole fitness tracker, then make a timeline.
From that data, you can see how to take out entries of logs, web browsing…
Than from that, you can build up a timeline and get a full picture of what the person’s been up to.
Also location information can be decanted from the devices in our pockets and on our wrists.
In other words thanks to the ubiquity of smart personal devices, it seems inevitable that there will be an increase in data from such devices being considered for use in criminal investigations or prosecutions.