I just put one of my hiking sticks within easy reach & push off of it.
At work there is a desk within reach (I don't have a desk job, just a desk) that I often push off of.
At home (inside) I'm only about 12" off of my bed, so getting a swing going from that is easy.
The string is a good idea especially if you don't have: hiking sticks, desk or bed to push on. But what I want is an automated thing to swing me gently all night.
I thought about having a few of my slaves rock me gently, then I realized a critical flaw in that plan: I don't have any slaves.
LOL, didn't read your post before I wrote mine Seems great minds think alike.....or uh at least yours and mine does.