We are developing Colossal Magnetoresistive (CMR) manganite thin film bolometric sensors to be employed as total energy detectors for beam diagnostics of the Linear Coherent Light Source (LCLS) Free Electron Laser (FEL) (at the Stanford Linear Accelerator). LCLS is an ultra bright, ultra short coherent x-ray source whose peak brightness will exceed that of third generation x-ray sources by about ten orders of magnitude and average brightness by three orders of magnitudes. It is expected to produce 1012 x-rays per 200 fs pulse with a repeat frequency of 120 Hz through self-amplified stimulated emission. In characterizing the beam, it will be necessary to measure the total energy of the FEL pulse. The Advanced Detector Group at Lawrence Livermore Laboratory has developed a scheme for FEL total energy measurements based on bolometric detection and are collaborating with Towson University to implement such a detector using CMR manganite thin films. Here we discuss the basic scheme, results of simulations of the thermal response and the materials development efforts towards fabricating the thin film detectors.