This capybara scraper checks my bitcoin address at blockexplorer for an updated balance periodically and posts it to Beeminder.

gistfile1.rb

#!/usr/bin/env ruby
require "capybara"
require "capybara/dsl"
require "capybara-webkit"
require "beeminder"
require 'dbi'
Capybara.run_server = false
Capybara.current_driver = :webkit
Capybara.app_host = "http://blockexplorer.com"

module EAR
  class Client
  class BlockExplorer
  class Tester
    include Capybara::DSL
    
    def latest_transaction
      first=nil
      last=nil
      all(:xpath, "//tbody/tr").each do |tr|
        #puts "line: #{tr.text}"
        if first.nil?
          first=tr.text
        end
        last=tr.text
      end
      
      if first =~ /(.+)/
        first = $1.split
        #puts "first: #{first}"
      end
      # 1(txid) 2(blocknum) 3(datetime) 4(Received) 5(addresses addr addr) 6(amount)
      if last =~ /([0-9a-f]{10})\.\.\. (Block \d+) \(\d{4}-\d+-\d+ \d\d:\d\d:\d\d\) (\d+\.\d+) (Sent|Received): Address ((?:(?:[0-9a-zA-Z]{34}) )+)(\d+\.?\d*)/
        out ="#{first[0]} #{$1}\n"
        out+="#{first[1]} #{$2}\n"
        out+="#{first[2]} #{$3}\n"
        out+="#{first[3]} #{$4}\n"
        out+="#{first[4]} #{$5}\n"
        out+="#{first[5]} #{$6}"
      else
        puts "last (did not match): #{last}"
      end
      #puts "latest_transaction: (done)"
      #puts out
      out
    end

    def bitcoins(addr)
      begin
      visit("/address/#{addr}")
      rescue
        puts page.body
      end
      latest_transaction
    end
    
  end
  end
  end
end

class BlockChain
  def self::dbi_already(amt)
    DBI.connect('DBI:SQLite3:blockchain.sqlite', 'ruby', 'ruby') do |dbh|
      sql = "SELECT balance FROM latest_balance ORDER BY id DESC LIMIT 1"
      row = dbh.select_one(sql)
      #puts row[0]
      #puts amt==row[0]
      if row
        amt==row[0]
      else
        false
      end
    end
  end

  def self::dbi_submit(amt)
    DBI.connect('DBI:SQLite3:blockchain.sqlite', 'ruby', 'ruby') do |dbh|
      sql = "INSERT INTO latest_balance (balance) VALUES (?)"
      row = dbh.do(sql, amt)
      row==1
    end
  end

  def self::main
    #puts "Testing BlockExplorer"
    scraper = EAR::Client::BlockExplorer::Tester.new
    out = scraper.bitcoins('19bCjfcxrdEyPNoH6rxRhYGaRfmJ4yU3ND')
    #puts out # if @debug
    if out =~ /Amount\? (.+)/
      #puts "Amount: #{$1}"
    end
    if out =~ /Balance\? (.+)/
      bee = Beeminder::User.new "SecretBeeminderAPIkey"
    #  insert into latest_balance (balance) values (15.62305247);
      balance=$1
      if !dbi_already(balance)
        puts "Posting latest balance: #{balance}"
        bee.send "christmas-bitcoins", balance
        puts "WARN: Did not enter any update to sqlite" unless dbi_submit(balance)
      else
        puts "christmas-bitcoins: #{balance}"
      end
    else
      puts "FAIL: Did not get Balance from BlockExplorer"
    end
  end
end