Uncooled IR sensor technology has accelerated rapidly in the past few years. Higher performance sensor, electronics integration, and enhanced signal processing are generating new applications and increasing production volume. Uncooled sensor are being considered to replace cooled sensor in some applications, but most importantly, the unique characteristics of the uncooled sensor spawn novel uses of the technology. Very small, lightweight and lower power sensor are possible with the uncooled IR. However, moderate levels of performance are expected even from the smallest sensors. This demand for performance stimulates new ideas for thermal detector structures operating at or near the theoretical limit. This paper reviews the exciting new applications of the uncooled technology and investigates the novel technical approaches necessary to bring about a new generation of uncooled IR sensor technology.