The "BébéSounds Angelcare Movement Sensor" isn't new, but that's not a bad thing, especially when its retained such a healthy positive rating on Amazon — 4.5 stars out of five with over 300 reviews.
It distinguishes itself from regular baby monitors by the inclusion of a movement sensor. When the sensor is placed under the child, a small "tic" sound is transmitted every time the baby moves. If no movement is detected for 20 seconds, an alarm will sound. (The audible tic can be replaced with a light flash, as well.)
Why would you care to know every movement your baby makes? Many parents fear losing their child to Sudden Infant Death Syndrome, a mysterious crib death which can occur for reasons we don't yet understand. There's some thought that SIDS could be caused by children choking, breathing in their own exhaled CO2, or suffocating under blankets or loose clothing. Whatever the cause, some parents find the knowledge of their child's every move to be a comfort.
BébéSounds Angelcare Movement Sensor [Oh GIzmo!]