default to use ARGV[1..-1] (everything after calling the script)

pushover.rb

#!/usr/bin/env ruby
require "net/https"

url = URI.parse("https://api.pushover.net/1/messages")
req = Net::HTTP::Post.new(url.path)
req.set_form_data({
  :token => "abc123",
  :user => "user123",
  :message => "#{ARGV[1..-1].join(" ")}",
})
res = Net::HTTP.new(url.host, url.port)
res.use_ssl = true
res.verify_mode = OpenSSL::SSL::VERIFY_PEER
res.start {|http| http.request(req) }