FxPotatoWeb
Deployed to Heroku here.
Demonstrating the Foreign Exchange currency rates looker-upper. Potato style.
Uses last daily feed from European Central Bank, and exposes a simple interface to get the conversion rates for one currency to another on a given day.
Source code for the gem is here.
Running the site
Setup the site like any rails app, with a strong bundle install, and a npm install for good measure.
From there it should be a simple bundle exec rails s to get the app up and running locally.
Docker!
If you have docker and docker-compose installed, you still have to run the setup commands, but then a meagre rake docker_run will start the app up in a container with a postgres container buddy which it completely ignores.