When my son was an infant, he had the world's worst colic. The only time he would sleep when he was having a bad bout was in this little chair that vibrated when you wound it up. When the vibration would stop, he cried so we were up winding the seat a lot. Any new parent with a fussy baby knows that you will try anything to calm them down. Many parents find that a drive in the car gets them quieted down.
The bad part is that parents aren’t always up for a drive. Ben Heck has come to the rescue with a motion simulator he has built that goes onto a car seat to help the fussy baby get to sleep. Heck used the Google Android Open Accessory Development Kit (ADK) in the build to create a car seat from a viewer request that simulates the motion of a car seat in the car. The cool part is that the simulator actually captures the feel of the movement of the user's car and plays it back using simulation.
The motion is added to the car seat using test servos. I would have loved to have something like this when my son was little. It would have really saved me from some 2 am drives to get him to go to sleep only to have him wake up again when I pull into the driveway.