Once all of your filament from one type has been depleted (or close to),a re-order link (that you setup initially when you make the spool) is sent to you via the app/email, you click it, and the filament is ordered for you automatically. Alternatively, you could have it fully automated so the SP re-orders completely autonomously, and you never have to think about ordering filament again.
I understand this will be dependant on API’s and what website you’re using, but maybe you could find out what the requirements are to hook up SP to websites like ebay/amazon/sunlu/etc to create this auto-reordering system.
I wouldn’t want it to auto order, but it would be cool if I could have it send me an email or other notification when I’m down to a preset number of spools of a particular color. That email/notification could have a user set link for ordering more filament.