I’ve never been that thrilled with them. The one on our BMW has a failed lock button, and it’s over $200 to replace. But here’s another problem:

The teenagers, he said, likely got into the car using a relatively simple and inexpensive device called a “power amplifier.”

He explained it like this: In a normal scenario, when you walk up to a car with a keyless entry and try the door handle, the car wirelessly calls out for your key so you don’t have to press any buttons to get inside. If the key calls back, the door unlocks. But the keyless system is capable of searching for a key only within a couple of feet.

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.

Mr. Danev said his company was in talks with several car manufacturers to install a chip that can tell how far the key is from the car, thereby defeating the power-amplifier trick.

I’d think that putting the key in the microwave would work as well as the freezer, except you risk accidentally cooking it. That wouldn’t be a problem with our new unit, though — it won’t let you start it without opening and reclosing the door.