Which statement is NOT true about external objects?

The statement regarding the use of external objects in formula fields is not accurate. External objects can indeed be integrated into Salesforce in ways that allow different functionalities, but they are not usable in formula fields in the same way standard and custom objects are. This limitation arises because external objects reference data outside of Salesforce, which affects their compatibility when it comes to formulas that typically operate on internal Salesforce data.

The other statements reflect true capabilities of external objects. They can integrate with Salesforce APIs, Apex, Visualforce, and Chatter, allowing for a seamless connection between external data and Salesforce functionality. Additionally, external objects can be related to other objects, providing a way to establish relationships even when the data resides outside of Salesforce. Furthermore, external objects are automatically available in the Salesforce1 mobile app, ensuring that users can access relevant external data on mobile devices without needing additional configuration.