Can use index by pinyin with English language setting on iPhone.

add_pinyin_to_vcard.rb

require 'rubygems'
require 'chinese_pinyin'
 
name = []
cp = false
 
def p(z)
  pinyin = Pinyin.t(z, '')
  pinyin[0] = pinyin[0].upcase
  pinyin
end
 
ARGF.readlines.each do |x|
  if cp and (not (/X-PHONETIC/ =~ x))
    if name and name.length == 2
      puts "X-PHONETIC-FIRST-NAME:#{p(name[0])}"
      puts "X-PHONETIC-LAST-NAME:#{p(name[1])}"
    elsif name and name.length == 1
      puts "X-PHONETIC-LAST-NAME:#{p(name[0])}"
    else
      raise "ERROR NAME FORMAT #{name}"
    end
  end
    
  cp = (/FN:/ =~ x)
  name = x.split(':')[1].split(' ') if cp
  
  puts x
end

1. export contacts to cards.vcf file from Concats application.
2. execute sudo gem install chinese_pinyin
3. execute ruby add_pinyin_to_vcard.rb cards.vcf > new_cards.vcf
4. inport (update) new_cards.vcf to Concats application.
5. index contacts by pinyin from English lunguage setting.

在Mac OS X 10.12.4上运行会报：
/Library/Ruby/Gems/2.0.0/gems/chinese_pinyin-1.0.1/lib/chinese_pinyin.rb:54:in translate': undefined method fetch' for "":String (NoMethodError)

系统自带的ruby版本：ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin16]