Could Xero grab a RSS feed periodically to enter invoices
Rather than having a system push data to Xero , Xero could be set to subscribe to an RSS feed that is in the correct format to add invoices.
This doesn’t fit with out API model.
personally i prefer the push option, i can't quite see any uses for this sort of thing. how do you suggest handling authentication on something like this ? you would also be at the mercy of xero's schedule as to when your invoice would appear in their system.