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