Integrate with various different HLR gateway protocols which are then normalised and exposed as standard interface and API to your customers.
Provide a billable service to customers where they are able to do bulk HLR lookups of CSV files from the dashboard or via API.
Check the active status of a number before sending an SMS and only send if the number is returned as active. This can be enabled per SMS gateway.
Set a validity period for cached results to avoid duplicate HLR look ups.