Apr 5, 2021 SOMERVILLE, Mass. (WBZ NewsRadio) — A new smartphone app created by the state will let you know if you've been exposed to COVID-19. The app, called "MassNotify," will let users opt-in to a system that will tell them if they were around a person who tested positive. Each user downloads the app on their phone, and enables Bluetooth, which reaches out to other phones that have the app in the user's area. The app was developed in partnership with Google and Apple, and is available on Android and iPhone. When someone tests positive, they anonymously let the system know, and the app warns people who may have been in close proximity.