The present invention relates to devices and methods for conveying power and/or data signal along a wellbore bottomhole assembly (BHA) having a steering unit, a bidirectional data communication and power (“BCPM”) unit, a sensor sub, a formation evaluation sub, stabilizers. A power and/or data transmission line enables power transfer and two-way data exchange among these BHA components. In one embodiment, a drilling motor includes a transmission unit that transmits power and/or data between modules adjacent the motor via conductive elements in the rotor and/or the stator. A power/data transfer device is adapted to transfer power and/or data between the rotating and non-rotating sections of the transmission unit. The tooling and equipment making up the BHA can be formed as interchangeable modules. Each module can include electrical and data communication connectors at each of their respective ends so that power and data can be transferred between adjacent modules via modular threaded connections.