A remote sensing unit for sensing subsurface formation is provided. The remote sensing unit is an active device with the capability of responding to control commands to determine subsurface formation characteristics, and transmitting corresponding data values. Some embodiments of the remote sensing unit include a battery, or a capacitor for storing charge. The embodiments that include the capacitor receive RF power that is converted to a DC signal for storing charge on the capacitor. When the charge is depleted to a specified point, the remote sensing unit prompts the wellbore tool to transmit additional RF power to recharge the capacitor. The remote sensing unit is provided with RF power to wake it up and to place it into an operational mode, and/or to send modulated data values that are then transmitted to the surface where operational decisions for the well may be made.