Why isn't it possible to just use your iPhone or any other Bluetooth (4.0 low energy) device, they should have a unique mac address and could be used for something like this.
iPhones have this habit of running out of battery. That could be inconvenient. The battery in the key fob probably lasts on the order of months because that's its only purpose in life.
That's one way of seeing it... Usually when I am at work or work with my Mac most likely my phone is either with some decent battery % or being charged.
So if I leave for a few min, my phone usually always goes with me thus will work fine without another device.
How/why is this better?