Just a personal observation after swapping between smartphones during the last few weeks.
I tend to keep my smartphone in the same pocket as the fob for the Prius when I am approaching the car. Once inside the car I take out my phone and put it in one of the drink holders in the centre console before I push the button to start up the car. However, from time to time I do find that I am unable to unlock the Prius when I have my smartphone still in my pocket. All I usually need to do is put my hand on the handle and the car should unlock.
In a nutshell, keyless entry for automobiles will tend to use the unlicensed 2.4GHz spectrum used by Bluetooth and some flavours of Wi-Fi which means that it will be susceptible to interference from such devices particularly if they are immediately adjacent and broadcasting. What things will come down to is which device is broadcasting the stronger signal and whether or not there is enough signal to overcome the noise created by other signals on the same band.
So, if you’ve ever wondered why your keyless entry doesn’t work or perhaps why your car won’t start up try separating your Bluetooth-enabled smartphone from the car fob and that should fix things up for you.