This scout plugin give info about ssl cert, which installed on web server. You can create trigger, which will notify before ssl cert expired.

scout_simple_check_ssl.rb

require 'net/https'
require 'uri'

class SimpleSslCheckPlugin < Scout::Plugin
  OPTIONS=<<-EOS
    url:
      default: https://localhost
  EOS

  def build_report
    uri = URI.parse(option(:url))
    http = Net::HTTP.new(uri.host,uri.port)
    http.use_ssl = true
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE
    http.start do |h|
      @cert = h.peer_cert
    end
    
    report(
      subject: @cert.subject, 
      issuer: @cert.issuer,
      serial: @cert.serial,
      issued: @cert.not_before.to_i,
      expires: @cert.not_after.to_i,
      days_left: ((@cert.not_after - Time.now) / 86400).floor
    )
  rescue => e
    error("Some error: #{e.inspect}")
  end
end