Ruby

Using Net::HTTP (no dependencies)
require 'net/http'
require 'uri'

PING_URL = "https://watchcron.com/ping/your-uuid"

def ping(url)
  Net::HTTP.get(URI(url))
rescue => e
  $stderr.puts "Ping failed: #{e.message}"
end

ping("#{PING_URL}/start")

begin
  run_backup
  ping(PING_URL)
rescue => e
  ping("#{PING_URL}/fail")
  raise
end
Rake task
task :cleanup do
  ping("https://watchcron.com/ping/your-uuid/start")

  ActiveRecord::Base.connection.execute(
    "DELETE FROM sessions WHERE updated_at < NOW() - INTERVAL '30 days'"
  )

  ping("https://watchcron.com/ping/your-uuid")
end