You will see a yaw condition within ForeFlight's Synthetic Vision while connected to a device that provides AHRS data. The display does not have an inclinometer, which is recognized as the "ball in a tube." Instead, the yaw indication will be displayed as a shift in the terrain display.
NOTE: Starting with ForeFlight Mobile version 6.7, for the yaw feature to work, you must be moving. You will not be able to use the yaw feature while stationary.