Decenders
After the Piper Alpha disaster, we got decender things offshore which I can't remember the name of.
It consisted of a thing that resembled a baby's nappy which you stepped into, then the mechanism connected to a ring on the front. A rope hung in a bag at the side. This rope came up through the mechanism and you attached the end to a strong point on the rig. As you stepped off, the rope fed out of the bag and as it passed through the mechanism, it slowed your rate of decent. It was possible to grab the rope, and with modest additional downward pressure, to stop completely. The theory was that you stopped just above the water where you would be seen by rescuers in a boat, and it would be a simple matter for them to pluck you off like apples.
Luckily, I never had to try it in anger, but I do remember leaping (?) off a scaffold tower in a warehouse while being trained in it's use. I remember being quite impressed with the thing - if only I could remember what it was called.