To use the BAC, you simply fold out the straw and exhale into it for a full 5 seconds. Five seconds later you know whether it’s safe to drive home or you need to call a cab. The FM transmitter allows you to manually adjust the frequency being broadcast, and this is displayed on the LCD display.
At around $80, it’s twice as much as a standard FM transmitter, but we think the functionality is worth the extra moolah.
You can buy one from here.