Flower is a handy tool for monitoring Celery processes. As it's build on top of Tornado web server it needs it's own outside facing port and can't be run as part of your regular Heroku app which only provides one web process type. Luckily Flower is really easy to install as another app and can be run free of charge on Heroku.
This project template/guide helps you to bootstrap the process and creates a simple app for running Flower.
Clone the repo:
git clone https://github.com/Tesorio/celery-flower-heroku.git
Create an Heroku app:
heroku create APP_NAME
You will need to set the following environment variables (read more about auth here https://flower.readthedocs.io/en/latest/auth.html):
BROKER_URL FLOWER_OAUTH2_KEY FLOWER_OAUTH2_REDIRECT_URI FLOWER_OAUTH2_SECRET
Push to heroku:
git push heroku master
Now visit the app.