When interacting with APIs that require secret keys, it's best to create a web service that you control in order to keep the keys private. We can do so by creating a small service ("microservice") using NodeJS and deploy it using Now.
npm install
# Without environment variables
npm start
# With environment variables
APP_ID="app_id_value" npm start
now
# Environment variables
now -e APP_ID="app_id_value"