bibtools - 0.1
Install:
pip3 install bibtools-pkg
Fetch PubMed Central for open-access papers as well as Sci-Hub
bibtools -i PMID # Single PMID
bibtools -i PMID1,PMID2 # Comma-separated PMIDs
bibtools -l pmids.dat # List file of PMIDs, one per line
bibtools -i PMID -b # Generate bibtex from MedLine json
bibtools -i PMID -p /path/to/directory # With custom storage path. Default is current working directory
While untested, may work with DOIs and other unique identifiers.