With the smartphone apps for location and contact tracing being normalized for fighting coronavirus, it opens up space for using the same techniques to fight other diseases.
HIV, Syphilis, and drug resistant gonorrhea are obvious candidates because they do not have non-human hosts.
Instrumentation would be easy. Generate a database entry when an individual is diagnosed with one of these pathogens, acquire phone data via disease surveillance authorities, use machine learning directed at that data to identify plausible intimate contacts, and send notifications with testing requirements, thrown against a database of most recent tests.
Mandate response (in the usa this would be analogous to a subpoena) to a notification (appearing at a clinic for testing and treatment) and enforce it as aggressively as corona isolation.
From an ethics standpoint, if app based corona tracing is ethical, this is ethical too. From an effectiveness standpoint, this would likely aid in the eradication of two scourges (Syph, GC) and the close control of a third (HIV).
Please let me know why I'm wrong, or alternatively, if this could be expanded even further to trace other social ills.