Hello Jacob !
When there is standard business object BUS1240, why should use custom business object ?
Delegate this business object and create an event. On adding a person check any infotype gets updated or change document is created.
If so, link this custom event with respective infotype/change document and get the workflow triggered.
If no change document is created, either you can go for custom change document or create an implicit enhancement or try the BAdI BADI_EHSI_IH_STATUS_SWITCH to trigger the workflow.
Regards,
S.Suresh.