I was with you up to the last item. The iPhone app is better for running engines, the iPad app controls the layout. The Legacy Flyer from Lionel is great.
I was not aware any of the Legacy Flyer engines had the transmitters installed to activate the sensor tracks. If they do then I will be adding the sensors to my S gauge track. Can you elaborate on the functionality you are getting with the sensor and Flyer Legacy engines? Thanks for posting this.