Business processes have been long researched, with many tools, languages, and diagrammatic notations having been developed for automation. Recently, distributed ledger technology (of which Blockchain is one type) has been proposed for use in the monitoring of business process compliance. Such a set-up is attractive since it allows for immutability and thus a perfect record of the history of the business process regulated.As blockchain platforms mature and their applications increase, one can observe that instead of having one blockchain as a ‘one world computer’ multiple blockchains will co-exist while possibly interacting. Existing work for business processes within the blockchain domain have focused on single isolated blockchain implementations. In this paper, we do away with this severely limiting assumption and propose a method to monitor business processes spanning different blockchains and other off-chain servers. We apply this work to business processes expressed in BPMN along with annotations proposed for a blockchain context. We further describe how we handle blockchain interoperability by synthesizing automatically off-chain monitors, acting as notaries, that handle message passing between blockchain systems, and how we employ hash-locking for cryptographically secure token swapping.