In a collaborative effort, Apple and Google have developed an industry-standard detection feature called “Detecting Unwanted Location Trackers” (DULT) for Bluetooth trackers. This standard allows users on iOS and Android devices to be alerted if an unknown Bluetooth tracker is monitoring their location.
Google is buying your data, not selling it. They use it to make their ad platform more effective, and selling the data would just help their competitors.
The NSA does collect data from third parties like Google, but not just anyone can buy it from them.