Possibility to index non-entity data

Problem/Motivation

I would like to index data to Elasticsearch from an external API.

Currently it seems that Elasticsearch Helper supports only indexing of entity data from the database. Is there some way to index data to Elasticsearch directly from an external API. I would not like to create this data as entities in the Drupal database. It would be handy to get this indexing happening with the same Elasticsearch Helper API, so I don't need to run separate Drush command for indexing the entities and the external data.

It would also be nice that I could utilise the plugin architecture of Elasticsearch Helper and use it's methods so that the project would have only one way of doing the indexing.

Thanks for a great module!