These tracking apps need people to "opt in" to say they are infected. Additionally you have to have the GPS on your phone and allow the app to access the GPS. They use public/private key pairs so you are anonymous and there's no way to reverse that anonymity.
It will also only work with others who are enrolled. If you don't enroll, you don't have the public/private key pairing to be told or submit.
That said, this is scary, but if you have a phone and haven't gone through security settings to turn things off, your phone is ALREADY doing 90% of this.
