Hi Paul,
Does the export_statistics utility help with providing what you are looking for? The utility provides metrics on ingestion at a datasource level. Run periodically and calculate the delta, a 0 value means nothing ingested.
https://www.ibm.com/support/knowledgecenter/en/SSPFMY_1.3.2/com.ibm.scala.doc/admin/iwa_admin_stats_ovw_c.html