ok, so for years with a physical key plus "remote clicker", I always had a fail safe system if I lost my keychain. I kept a "flat" key that could start the car taped to a card in my wallet. I also kept a backup clicker hidden in the car. Never had a problem, it saved me a few times, believe me. I;d have to lose my keys and wallet to get locked out.
Now w/the "smart key"......I understand there's the "mechancal" thin metal key that I can slip out and maybe keep in my wallet. But that only opens the door, right? You still need the keyfob, even if the battery is dead, to hold next to the the start button to start the car.
So let's say I want to hide a 2nd keyfob somewhere in the car. If the key fob is "on", it will fool the car, and doors wont lock, anyone can start car, etc. If I use the procedure to "power off" the key fob to save battery, can I keep it under a seat or in a storage area?
Or do I have to remove the battery? ( I will buy a 3rd key so I have one in my apt, one in the car, one in my pocket). Or will the car STILL know the keyfob is in the car? (I think not...}
You can try and remove the battery and see if that works. When the battery dies on those things, it can still start the car by placing the key frob against the POWER button. The transmitter behind the button induces a small amount of voltage to the frob, enough to communicate with the smart key. Not sure if this works with the battery removed, but it works when the battery is dead.
You can put your spare SmartKey in a metal box (Altoids mints) and hide that inside the car. The metal should block the signal. Or, as you said, remove the battery and then hide the SmartKey, and keep a spare mechanical key in your wallet.
I power off my second smart key FOB and keep it in my luggage (as a spare) when I go on long trips. Battery removal not required. The RAV4 does not recognize it's in the cabin.
I do keep it in an old bluetooth headphone case to prevent an accidental button push.
For my 2013 Limited, these were the instructions. It's called battery saver mode.
Press "unlock" twice while pressing and
holding "lock". Confirm that the electronic
key indicator flashes 4 times.
While the battery-saving mode is set, the
smart key system cannot be used. To
cancel the function, press any of the elec-
tronic key buttons.
My wife's Prius smartkey battery needed to be replaced at about 18 month, but it takes a CR2025 battery which has less capacity than the CR2032 in the Rav4.
I had the same apprehension as OP when I bought my Corolla with smart key in 2009. I even carry a spare fob battery in car for "just in case". Never have to use it. I change battery every 2 years. It's in the same bunch as my house key so I always have it.