There’s a small habit I picked up after a family member bought a car with keyless entry. He used to leave his keys on a shelf beside the hallway window, so we tried keeping them in a Faraday pouch instead. The interesting part was testing whether the car would still respond when the keys were inside. A properly made pouch should block the fob's radio signal, although the quality of the lining and stitching matters quite a bit. I also found some useful background information while reading about electronic security devices, including this page about an eas jammer, though that's a different type of equipment and not something I'd recommend for protecting car keys. My advice would be to test the pouch regularly and keep spare keys protected too.
