A free Siri/Cortana/Alexa clone,
This will fail for the same reason the Google Earth clone failed, the sheer power required to run it.
These are not, "oh lets put 10,000 possible queries into a server. and that's done".
Lets take a basic query
"Hi, where is the nearest petrol station"
So first up it needs to understand what you have just said, No easy task in itself.
Location Data for person requesting:
It needs to know where you are now, right now, not 3 weeks ago.
Location Data for requested service.
It needs to know about every petrol station, in every country. Updated constantly.
Basic bit, but it needs to know that the nearest one open at 3am is not the one you are closest to. Oh and you're on a motorway, so the closest, open at 3am may not the closest to you, but the closest by road.
"Now remind me to get the milk from Sainsburys on my way home."