The latest official release of bgcnv is available via:

Because really... What's the point of knowing your BG value in units of mg/dL or mmol/L if you can't easily convert it between the two units of measure? Thus, everyone needs a friendly blood glucose converter!

This release of bgcnv changes the quiet output format so it's more friendly:

% bgcnv 180 ; bgcnv -q 180
180 mg/dL ~ == 10.0 mmol/L
180 (~ 10.0)

% bgcnv 10.0 ; bgcnv -q 10.0
10.0 mmol/L ~ == 180 mg/dL
10.0 (~ 180)

There's also a Web version of the bgcnv command. See Bgcnv Web to give it a go if you like. Here's to the worldwide Diabetes Online Community (#DOC)! :^)