The Guided Workflow capabilities are specifically intended to access SAP transactions. But ... the model that we use in Guided SAP Workflows is generally applicable to any external system that exposes a web interface. The Guided workflow component builds an iFrame inside of the BPM UI and that iFrame is the "window" into the SAP transaction. It could just as easily be some other external system. All that would be necessary is to build the URL in a way that works with the intended target system rather than building the URL for the SAP environment.