I allow Google Maps to keep track of my phone. I'm not too bothered about how or what they use this data for - it is often interesting to look back over a month and recollect where I have been. I am often stuck by the accuracy of this tracking, even at times telling me what shop I went into.
According to latest map - I have been to one place: Dublin. When I drill into this it show locations around where I live - I guess most others who are obeying the Lockdown will have a similar experience. Covid-19 Tracking Apps may have a role in the near future in the fight against the virus using technology similar to Google Maps. Of course not all people will have smartphones, many who do have tracking turned off - in the end it might just be a small proportion of the population who will do this. My mind is made up to get the tracking app when it becomes available - it might only be a few bytes in a vast lake of data, but every little bit helps!