iPhone Push Notification When Crypto Currency Meets Threshold

Prowl Image

If you would like to send yourself push notifications when one of the crypto currencies you are watching hits a certain threshold and you want to play around with a little coding, this is for you!

We will be using Ruby and the free application Prowl.

The first thing we need to do is setup a Prowl account and download the Prowl app from the App Store.

Creating an account.

Visit Prowl App and create an account.
Once your account has been created, click on the API Keys tab
to access your api key. You will need this to send push notifications to your iPhone.

Download Prowl from the App Store

Prowl App in the App Store

On Your Computer

Now to the fun part! Ruby has came pre-installed on the Mac for awhile now so unless you have a very old computer, you should have it. We will proceed in the assumption that ruby is installed.

Open up the Terminal application. You can find it here:
/Applications/Utilities/Terminal.app

There is a Prowl gem that we will be using from Ruby.
Install it with the following command.
sudo gem install prowl

The following is a Ruby script that will run every five minutes and send a push notification to the Prowl app on your phone if the price of Steem drops below .14 cents.

Save this text to a file and name it like get_price.rb.
Add your apikey.
Change the application name to your liking.

Run the program like so:
ruby name_of_file.rb

To stop the program:
control + c

Enjoy!

  require 'json'
  require 'net/http'
  require 'uri'
  require 'prowl'

  def number_for(float)
    "$#{float.round(2)}"
  end

  alert_price = 0.13999
  crypto = 'steem' # could be any that cryptonator supports
  url = "https://api.cryptonator.com/api/ticker/#{crypto}-usd"
  uri = URI.parse(url)

  while true do
      res = Net::HTTP.get_response(uri)
      price = JSON.parse(res.body)["ticker"]["price"].to_f
    
      # Log information while the program is running.
      puts "#{number_for(price)} at #{(Time.now.utc).strftime("%Y-%m-%d %H:%M")}"
    
      if price <= alert_price
        Prowl.add(
            apikey: "your-api-key",
            application: "Whatever Name You Want",
            event: "changed",
            description: "#{crypto.capitalize} price down: #{price}"
        )
      end
      sleep 5*60
   end