Saving player name throughout script-launches
I'm not sure why you are reading all of the file and checking for istitle(). Here I make the assumption that if the file exists, it will always include the player name on the first line.

if os.path.isfile('names.json'):
  with open('names.json') as f:
    player_name = f.readline()
else:
  player_name = console.input_alert('What is your name? ').title()

with open('names.json', 'w') as f:      
    f.write(player_name)


If you want to read the entire file and check for istitle():

player_name = None
if os.path.isfile('names.json'):
  with open('names.json') as f:
      for line in f.readlines():
          if line.istitle():
              player_name = line

with open('names.json', 'w') as f:  
    if player_name is None:
      player_name = console.input_alert('What is your name? ').title()
    f.write(player_name)


You may notice that I do not close the files in either case. That is because the with statement takes care of that for us. See Understanding Python's "with" statement.