Recent advances in current-pumped, bandgap-engineered semiconductor lasers have dramatically impacted laser-based sensor concepts for in-situ trace species measurement and standoff sensing applications. These devices allow a common technology platform to access strong fundamental vibrational absorption transitions of many gases, liquids, and solids in the mid-wave and long-wave IR, as well as far-IR, or THz. The THz wavelength region is particularly interesting for applications related to structure penetrating detection of hidden materials and biomolecular spectroscopy. This presentation will briefly review the important properties of these lasers as they apply to sensor design and present highlights of recent sensor development activity for trace gas analysis in environmental and biomedical applications, remote sensing LIDAR systems, and detection of hidden explosives.