The reality is, as much as you may like to deny it, just about any possible information about you is already out there in the marketplace. If you have a mobile phone, use social media, post on websites (like this one), use Google, buy from Amazon, there is very little someone can't find out about you. And they don't need a warrant, they just have to pay for it.
I can post a property on facebook, and pay them to send it to people in a certain postcode, aged between 30 and 40, with an income over $80k who are in the market for a house, and that's at the most basic level. Big companies with more money can target people much more accurately. And that's not touching what your phone, online browsing etc can tell about you. Those of you very precious about your privacy would be horrified. Knowing who you've been close to is pretty minor by comparison. Anyway, I will certainly be downloading it. I have a chronic respiratory condition, and will be very pleased to be advised when I have been in contact with COVID-19. I hope it's not one of you guys, because then I won't have that information.