An anti-theft device monitors bottles. It is comprised of a two components hingably connected together. They can move from an open position to a closed position to enclose the neck of a bottle. One component has a first latch element and contains electronics including switches. The other component has a second latch element. The latch elements combine to hold the two components in the closed position. When the two components are moved to the closed position, and a bottle is in position, the bottle contacts elements which in turn change the states of associated switches. One of these elements also functions to retain the bottle on the tag. The anti-theft device may be armed or disarmed by remote devices. The latching elements may be releasably lockable such as by a magnet. The anti-theft device may have passcode protection capabilities.