Custom Fields for products / packages that are pre-defined by the owner / admin.

 

An example would be a simple status where products can be assigned an online, maintenance, offline status and you can handle requests to said product accordingly depending on status.

 

(Using the REST API to check if a product is online and functioning but currently custom fields can only be used to control product stock levels).

HEAR HEAR! So surprised to see that Invision has ecommerce but no custom fields defined by admin...