sample crowdflower webhook endpoint

config.ru

require './webhook'
run Sinatra::Application

Gemfile

source :rubygems

gem "sinatra"
gem "json"

gistfile1.txt

#To test, run the following to ensure the puts statements are being logged

heroku config:add LOG_LEVEL=DEBUG
heroku logs

#Then hit the following url to test the webhook directly (replace your webhook and job_id):
https://crowdflower.com/jobs/67977/webhook?job[webhook_uri]=http://furious-dusk-7697.heroku.com/endpoint

webhook.rb

require 'rubygems'
require 'sinatra'
require 'json'

post "/endpoint" do
  success = true
  if params[:signal] == "unit_complete"
    payload = JSON.parse(params[:payload])
    puts payload["results"].inspect
    #answer = payload["results"]["name_of_field"]["agg"]
    #do something with answer
  end
  success ? 200 : 500
end

Great i was looking for the actual response you crowdflowder sends but this helps, in their docs they dont show how the results json look like they just show array below, it seems that they have changed the json format.
{
"results": {
"judgments": []
},