Basically: When you exhibit symptoms, think about everyone you've been in contact with over the past $INCUBATION_PERIOD and warn them to self-isolate.
Significant success in controlling outbreaks in Taiwan, Singapore, South Korea using digital contact tracing in addition to traditional approaches
Bluetooth is not all that good a proxy for exposure. It goes through walls and can't tell how far away you are
Need significant penetration (maybe as much as 80% of the population), and people are largely unwilling
False positives will amplify the already severe shortage of tests
Models of transmission are still unclear, can't tell whether proximity is determinative
Location data is a bad idea, very difficult to de-identify. Probably not super useful anyway as GPS is not that precise and isn't good at telling how far apart people are inside buildings
Proximity data is better (probably Bluetooth), still some concerns about re-identification
Privacy and security risks can be mitigated (Hart, V.: Outpacing the Virus: Digital Response to Containing the Spread of COVID-19 while Mitigating Privacy Risks)
DP3T: Decentralized Privacy-Preserving Proximity Tracing
Poor and racialized communities bear the brunt of pandemics already
Apple/Google CT systems will rely on low-power Bluetooth, which many older phones don't have
State holding data is differentially risky
More likely false positives: Poor and racialized people live in close quarters, small apartments; work high-contact jobs
False positives are more harmful for the poor: need to stop working
Also more harmful for racialized people: quarantine orders probably backed by state violence, differentially risky
Must be opt-in, cannot be a condition of access to any benefit
Data must be completely single-purpose
Pilot program watching for inequities