A
very powerful homing device used by Bond to follow
Goldfinger's
Rolls Royce from a distance. The transmitter's frequency could be picked
up by the receiver in 007's specially modified Aston Martin DB5.
The
homing device's smaller brother fits neatly into the heel of Bond's shoe
so that he can be tracked down when deeply entrenched in an undercover
operation. In "Goldfinger", 007 tries to use it to send a coded message to
his allies, but his note never gets to Felix Leiter.