New in box! This is a wireless AngelCare movement sensor, to be paired with any baby monitor. The square sensor is placed under the crib mattress and is VERY sensitive to baby’s motions, detecting breathing, squirming, etc. The alarm beeps once when no motion has been detected in so many seconds as an attempt to rouse baby, then beeps non stop of baby is still not moving. Couple seconds later until movement is sensed or it is turned off by you. Similar to the owlet sock, but cheaper and no worries about it getting kicked off! We had a wired one with monitors with our older kids that wore out so we bought a new version for the new baby, but baby didn’t want to sleep in the crib, so it didn’t get used, just unboxed and tested. It’s now back in the box and ready for the next home! Listed for $140 on Amazon, selling for $100 OBO. Moving and need gone before Saturday, so bring your offers! Clean, smoke-free, pet-free home. This is the sensor kit only, no audio or video monitor included, as listed on Amazon for $139.95