There's a product: http://www.lolaloo.com/en/

Motors and gears are loud, likely too powerful (and dangerous), and may not be fast enough to allow closed loop phase control. I once coupled a wiper motor with lever via a long spring to a baby's hammock. It worked OK, but it's not an oscillation, it's noisy, and it's dangerous.

I'd consider a super-sized version of a "beckoning cat" (and lots of similar toys) that essentially is a pendulum with a magnet and simple circuit to give it an electromagnetic push. This would not need a microcontroller, but it may be implemented with one.

There's a product: http://www.lolaloo.com/en/

Motors and gears are loud, likely too powerful (and dangerous), and may not easily match the required speed range. I once coupled a wiper motor with lever via a long spring to a baby's hammock. It worked OK, but it's not an oscillation, it's noisy, and it's dangerous.

I'd consider a super-sized version of a "beckoning cat" (and lots of similar toys) that essentially is a pendulum with a magnet and simple circuit to give it an electromagnetic push. This would not need a microcontroller, but it may be implemented with one.