What it actually does
Relay attacks are how a depressing number of modern cars get nicked. One thief stands near your front door with a device that picks up your key fob's signal, a mate stands by the car amplifying it, and your car thinks you're right there. Gone in under a minute. A Faraday cage box like this one simply blocks that signal entirely. No signal, no relay, no theft. Straightforward.
The Yale box holds up to 7 keys, which is handy if you've got a household with multiple drivers. It's a small, fairly solid little unit. Nothing flashy, but that's fine. You're not buying it for aesthetics.
Who this is actually for
Anyone with a keyless entry car parked on a street or near the front of the house should honestly consider one of these. If you drive something older with a physical key, you can scroll on, this isn't for you.
My neighbour lost his BMW to exactly this kind of theft last winter. Keys hanging on a hook inside the hallway, car gone by 3am. A £13 box would have changed that outcome.
One honest reservation
There's no price comparison here because this is the going rate for a decent Faraday box. Some cheaper unbranded ones on Amazon don't actually block signals properly, so Yale being an established brand does carry some weight. That said, it's worth testing your own box when it arrives: put a key inside, close the lid, and try to unlock your car. If it doesn't work, the box is doing its job.