An article discussing a radio amplifier used to steal cars

http://boingboing.net/2015/04/16/17-radio-amp-lets-thieves-ste.html

"If your car has a proximity-based ignition fob that lets you start the engine without inserting a key, thieves on the street in front of your house can use an amp to detect its signal from your house and relay it to the car, getting away clean.

The amps are pocket-sized, battery powered and cost as little as $17 on Ebay and Amazon.

Mr. Danev said that when the teenage girl turned on her device, it amplified the distance that the car can search, which then allowed my car to talk to my key, which happened to be sitting about 50 feet away, on the kitchen counter. And just like that, open sesame.

'It’s a bit like a loudspeaker, so when you say hello over it, people who are 100 meters away can hear the word, "hello,"' Mr. Danev said. 'You can buy these devices anywhere for under $100.' He said some of the lower-range devices cost as little as $17 and can be bought online on sites like eBay, Amazon and Craigslist."