By app I assume you mean using a smartphone/tablet as the remote control. This sends wireless commands via WiFi. MTH DCS engines do not directly "understand" WiFi so you need something to translate the remote commands to the DCS signals that the engines understand and which reside on the rails. The MTH Explorer and the MTH WIU/TIU combo can perform this translation.
The Z-1000 brick could provide the "raw" electrical power.