New Jersey and New York have both released free, surprisingly well-programmed COVID tracking apps, using the same Apple/Google privacy-respecting framework as many other state and national smartphone apps.
The app lets people check in with their health status, and be notified if someone nearby has been exposed (it does this in a rather complicated way that individual privacy, rather than reporting everyone’s location to the app publishers—as, say, pretty much any weather app does). For details, see Tidbits’ Former Apple Engineer: Here’s Why I Trust Apple’s COVID-19 Notification Proposal).
The app is easy to use, and provides a wealth of options described in this Tidbits article (which focuses on the New York version, but the apps appear to be identical other than the state). It’s free, user-friendly, and a quick low-risk download.