Multi-Cite is a pandoc filter which allows you to use multiple identifiers directly as references in Markdown.

It is current in early stages of development. It is conceptually similar to the doi2cite. It's key advantage is that it works with more identifiers: it should function with all DOIs (doi2cite just works with Crossref), and pubmed IDs. When complete it will add arxiv, and scrapped metadata from any URL via greycite.

Key disadvantage over doi2cite -- it's more complicated to use. It is written in python because it cannot be readily implemented as a lua filter (it uses Content Negotation for DOIs which lua filters do not support AFAICT). I have also decided to go the route of using dependencies rather than fit into core python, so it uses panflute and requests.