client.rb

module Bitcoin
  class Client
    include Singleton
    
    def initialize
      config_file = File.open(File.join(Rails.root, "config", "bitcoin.yml"))
      config = YAML::load(config_file)[Rails.env].symbolize_keys

      @client = JsonWrapper.new(config[:url],
        config[:username],
        config[:password]
      )
    end

    def method_missing(method, *args)
      @client.request({
          :method => method.to_s.gsub(/\_/, ""),
          :params => args
        }
      )
    end
  end
end

json_wrapper.rb

require 'net/http'
require 'addressable/uri'
require 'json'

module Bitcoin
  class JsonWrapper
    def initialize(url, username, password)
      @address = Addressable::URI.parse(url)
      @username = username
      @password = password
    end

    def request(params)
      result = nil

      full_params = params.merge({
          :jsonrpc => "2.0",
          :id => (rand * 10 ** 12).to_i.to_s
        })

      request_body = full_params.to_json

      Net::HTTP.start(@address.host, @address.port) do |connection|
        post = Net::HTTP::Post.new(@address.path)
        post.body = request_body
        post.basic_auth(@username, @password)
        result = connection.request(post)
        result = JSON.parse(result.body)
      end

      if error = result["error"]
        raise "#{error["message"]}, request was #{request_body}"
      end

      result = result["result"]
      result
    end
  end
end

util.rb

module Bitcoin
  module Util
    def self.valid_bitcoin_address?(address)
      # We don't want leading/trailing spaces to pollute addresses
      (address == address.strip) and Bitcoin::Client.instance.validate_address(address)['isvalid']
    end

    def self.my_bitcoin_address?(address)
      Bitcoin::Client.instance.validate_address(address)['ismine']
    end

    def self.get_account(address)
      Bitcoin::Client.instance.get_account(address)
    end
  end
end