This project supports collecting data of Vaillant system over VR900/920 via Smart API. Code is a bit outdated but should guide you to the right direction.
Do not query API too often, Vaillant keeps an eye on that and may disable your account. Already obersved that!
composer install;)- configure db
yii migrate/up
You need to setup a cronjob that runs every 5 minutes and executes php yii harvester/cronjob. Please note that php is YOUR correct php binary name (it could differ from my example).