(Related to this ME Resources topic about submitting and storing different units/measurements)
I found some interesting Drupal projects, that might be useful for Digits field. The topic is unit and measurement display and conversion. Useful for weights, length, sizes etc. Example: Recipes, RealEstate/Houses
Excerpt from description:
"Units API converts between various weights and measurements. The conversion uses the International System of Units (SI) conversion factors. Where possible, these conversion factors are those provided by the U.S. National Institute of Standards and Technology (NIST) Special Publication 811, 2008 Edition. If the NIST does not provide the conversion factor, other sources may be used as long as the work is GPL compatible."
For more details, have a look here: