They seem handy in a way but is there a battery that dies and you can't start the car?
Replacement cost?
I assume you still need to have the fob in your hand to unlock the door so what's the big benefit?
No, you don't need to have the fob in your hand, it can be in your pocket, laptop bag, backpack, man-purse, wherever.
The Toyota system works flawlessly. As soon as I used to put my hand on the door handle, it would open. Just my gentle touch would be enough for the car to react, no need to press a button. It was just like the car knew I was approaching. Touch the driver's side door handle, the door unlocks... touch the passenger side door handle, all doors unlock...
Then, press the start button while pressing the brake pedal, and vroom-vroom. Press the start button again, it shuts off. So simple.
As opposed as Mimico Polack, my current car doesn't have it and I miss it so much, I wish I could have it again.
My girlfriend has it in her Mazda6, I opened the fob it and it is made by Siemens AG (made in Munich). Toyota system doesn't say anything inside. The Mazda fob works a bit differently. I like the simplicity of the Toyota one.
Replacement cost for Toyota is close to $300, but you can get them for a lot less aftermarket, and program them yourself. They look identical.
For the Toyota one, the battery in the fob may die but the car warns you in advance, because the condition of the battery is continuously monitored by the car. A message appears on the information display screen that says something like "Your smart key battery is low. Please visit the Toyota dealer".