Android itself has one; it was pushed to all Android phones last summer.

I can confirm. Two of my devices had this shit on it. I didn't install it myself. I don't even live in Massachusetts. I notice that my Google settings menu has some Wuflu exposure notifications setting there. It is off. Nonetheless, you can't control it. I'm only surprised they left the app visible in the apps settings menu. I was able to uninstall it. At some point, Google will hide the app entirely. Speaking of which. What else is Google installing we aren't told about?