Ability to create "grouped fields" or "field collections"

It would add quite a lot of flexibility to the product if administrators were able to create "grouped fields" or "field collections". In other words, I would like to be able to create a custom multiple-value field consisting of 2 (or more) separate fields that are treated like a collection.

For example, consider a field collection named "Accessories" which would be made of 2 custom fields (one text field, and one number field). The text field would be named "REFERENCE" and the number field would be "NUMBER OF ITEMS". So the entire "Accessories" field could hold the following information:

• REFERENCE : AAAAA1
• NUMBER OF ITEMS: 2

---- * REFERENCE : AAAAA2

• NUMBER OF ITEMS: 5

---- * REFERENCE : BBBBB1

• NUMBER OF ITEMS: 3

---- * ETC.

It would be really neat if any custom field could be used in these collections. For instance, the Insight Object Field paired with a Number field, or a text field and a date field, etc. etc.