Additional Study Information: Adults 18 years or older, English speaking, who own an Android/iPhone smartphone and are willing to download an app and send/receive texts are needed for a research study to assess attitudes towards COVID-19 self-tests, self-testing, and a COVID-19 app. Both vaccinated and unvaccinated participants can participate in this study. Participants will come for an in-person visit where they will be shown how to test themselves with a COVID-19 antigen test and optionally self-test with study staff. They will also fill out a web survey on a computer which would take about 60 minutes to complete. Participants will be randomly assigned to two groups, with one group with access to the COVID-19 app and the other without. During the study, both groups will be sent text messages to submit their testing frequency weekly. All participants will be provided with 12 rapid COVID-19 home test kits, and be asked to track testing over four weeks. After four weeks, participants will return to take part in a final web-based survey, which will take about 60 minutes to complete. All in-person visits will take place at the ICAP Harlem Prevention Center, at 215 W. 125th Street, 3rd floor, Suite 302, New York, NY 10027.