Send iMessage messages with Quicksilver -- version 2. This version uses some Python to search a plaintext "phonebook" for non-email / non-phone number third-pane input (like a name). See the full post at http://n8henrie.com/2013/06/send-imessages-with-quicksilver-v2/

Create messages_phonebook.py

import os
import re
import sys

vcf_file = sys.argv[1]

def parse_file(infile):
    card = ''
    for line in infile:
        if line.startswith('BEGIN:VCARD') and card.endswith('END:VCARD\r\n'):
            yield card
            card = ''
        card += line
    yield card

iphone_count = 0
messages_phonebook = []
with open(vcf_file,'rb') as infile:
    for i, card in enumerate(parse_file(infile)):
        num_match = re.search(r'(?<=TEL;type=IPHONE)(.*?:)(.*)', card)
        if num_match:
            iphone_count += 1
            name = re.search(r'(?<=FN:)(.*)\r\n', card).group(1)
            number = re.sub(r'\D','', num_match.group(2))
            messages_phonebook.append((name, number))
            with open(os.getenv("HOME") + '/Desktop/messages_phonebook.txt','ab') as w:
                w.write('\n{}, {}'.format(name, number))

with open(os.getenv("HOME") + '/Desktop/messages_phonebook.txt','rb') as r:
    names_sorted = (name.strip() for name in sorted(r.read().splitlines() ) if name.strip() != '' )
with open(os.getenv("HOME") + '/Desktop/messages_phonebook.txt','wb') as w:
    w.writelines('\n'.join(names_sorted))

qs_messages.py

#!/usr/bin/env python

import sys
import re

script, name, phonebook_file = sys.argv

match = re.search(r'^\d{7}$|^\d{10}$|^(\d{3}\-)?\d{3}-\d{4}$|(^.+?@.+?\..+?$)', name)

# The input was a phone number or email, go with it.
if match:
    print name
    exit(0)

else:
    name = name.lower()
    with open(phonebook_file, 'r') as f:
        contacts_list = [ tuple(
            line.lower().strip().split(', ') )
            for line in f if len(line) > 1]

    for contact, number in contacts_list:
        if name == contact:
            print number
            exit(0)
        else:
            pass

# Returns the original name if no match was found.
    print name

Send with Messages.applescript

property appleID : "yourAppleID"
property path_to_python : "python3"
property path_to_qs_messages : "/Users/[username]/path/to/qs_messages.py"
property abs_path_to_messages_phonebook : "/Users/[username]/path/to/messages_phonebook.txt"

(*
See post at: http://n8henrie.com/2013/04/send-imessage-messages-with-quicksilver
Version 2 of the script at: http://n8henrie.com/2013/06/send-imessages-with-quicksilver-v2/

Send an iMessage to a buddy with Quicksilver.

Install by placing in ~/Library/Application Support/Quicksilver/Actions and restarting Quicksilver
First pane: type text to send.
Second pane: choose this action.
Third pane: pick buddy (iMessage number, iMessage email address, or their name if you've put it with their number into messages_phonebook.txt)
 *)

using terms from application "Quicksilver"
	on get direct types
		return {"NSStringPboardType"}
	end get direct types

	on get indirect types
		return {"qs.contact.phone", "qs.contact.email"}
	end get indirect types

	on process text firstPane with thirdPane

		if appleID is "yourAppleID" then
			display dialog "You need to open the \"Send with Messages\" Action script and set your Apple ID. Exiting."
			return
		else

			-- If the python part is set up...
			try
				set the_command to "PATH=/opt/homebrew/bin:/usr/local/bin:$PATH " & path_to_python & " " & path_to_qs_messages & " " & quoted form of thirdPane & " " & quoted form of abs_path_to_messages_phonebook
				set thirdPane to do shell script the_command
			end try

			try
				tell application "Messages"

					tell (first account whose (service type is iMessage and description is ("E:" & appleID)))
						login

						send firstPane to participant thirdPane

					end tell

				end tell

			on error a number b
				activate
				display dialog a with title "error with your QS action script"
			end try
		end if
	end process text

	on get argument count
		return 2
	end get argument count

end using terms from