Post on the Tesla subreddit claims that there
IS a key card and that you scan it on the driver's side B-pillar
Tesla Model 3 Screen and Key Card Seen Ahead of Launch - Tekopia
If this is the case, I'm pretty dumbfounded. I get that the Model 3 will be heavily integrated into the Tesla Network, but IMHO at the cost of Model 3 owners who have little to no intention with sharing the vehicle with anyone outside their household.
Scanning the key card or launching a mobile app to unlock the car (and possibly making it go) is like using an actual metal key and inserting into the lock of the car door, before remotes were even a thing. It doesn't make sense to me when economy cars have traditional keyless entry/start as an option, if not standard. Door unlocks when I grab it the handle, press a button to go, press again to stop, lock the car by touching the handle. Doesn't get much more simple than that.
Hopefully this post and I am wrong, and that a traditional fob is offered as a relatively inexpensive option, if not standard with the car like it should be.