That's called the Sports/Activity fob. I got one of those with my Volvo as well. Turns out that the key drains out pretty quickly if you use it regularly. I was using that one exclusively for a while and it died one day without much of a warning. Had to scramble to find my other keys! 😂I’ve got a new key where you leave one key in the car all the time and just carry around a small fob which the car recognises and the car opens when you touch the door handle
But yes, as others have mentioned, you do not need to leave your existing key in the car for this to work. And, of course, leaving the key in the car is pretty risky in any situation.