What techniques does the government use to try to find Montag in Ray Bradbury's Fahrenheit 451—and are they things used in society today?
In Ray Bradbury's Fahrenheit 451, there are several ways that the government tries to find Montag. First, there is the Mechanical Hound—which was already with them at the fire—a "tool" the firemen used when they were burning the houses of those with books, or chasing those people who tried to run away. The hound has a needle with a solution that it injects into its "victim" which numbs the person. Montag has killed his sergeant, Beatty. With this, the hound flies at him.
It made a single last leap into the air coming down at Montag from a good three feet over his head, its spidered legs reaching, the procaine needle snapping out its single angry tooth. Montag caught it with a bloom of fire, a single wondrous blossom that curled in petals of yellow and blue and orange about the metal dog...
After Montag turns the flame gun on the attacking hound, it is only able to partially inject Montag in the leg; numbed, the leg is useless, slowing him down when he desperately needs to escape. (Later, another Mechanical Hound will try to catch Montag again.)
There is not a Mechanical Hound in today's society, though there are weapons that shoot tranquilizers instead of bullets.
The other Salamander engines are roaring in the distance, looking for Montag, and the sound of police cars "cutting across town" comes to Montag. This would be similar to S.W.A.T. teams that are called out to pursue a criminal on the loose.
As Montag is running, he listens to the Seashell in his pocket that is blasting out news regarding the hunt for Montag:
Police Alert. Wanted: Fugitive in city. Has committed murder and crimes against the State. Name: Guy Montag. Occupation: Fireman. Last seen...
This would be similar to television news breaks today, information being transmitted on the radio, and perhaps even the spread of that same information on the Internet, either as a video or an online news article.
There are also helicopters in the sky, similar to those we have today (except in the story, they can turn into cars and then back into helicopters).
Some of the tools the government uses, as Bradbury describes them in his novel, are things that are a part of our modern society. Others are still only the result of his imagination, but may become everday elements of our world some day.