If you're wondering how the Canadian #COVIDAlert App works without collecting any personal information (including your location), it's actually super-clever.

If you install and activate the app, it will run in the background broadcasting random numbers at regular intervals using Bluetooth and listening for other phones that are also chirping out their own random numbers.

The app will record all the random numbers it hears and keeps track of all the random numbers it chirps out.
If someone tests positive for COVID, they can enter a special code provided form public health.

Then the app uploads the list of all the numbers it has chirped out to a server, which all the apps check daily. So another person's app will download that list of chirps associated with positive tests and will see if it has heard any of those chirps in the last two weeks.

(It also does some checking to see if your phone was close to the other phone and for a certain amount of time.) In the process, nobody collects, uses or discloses any personal information or any location data.

Here's where you can get more information and download the app: https://www.canada.ca/.../coronavirus.../covid-alert.html
The Privacy Commissioners of Canada and Ontario, at least, have the app on their phones, as do most of my fellow Canadian privacy advocates.

Sorry, here's the right link: https://www.canada.ca/en/public-health/services/diseases/coronavirus-disease-covid-19/covid-alert.html