I've been watching this thread with interest and have to say I wouldn't ever want to be tied to a cat. It just seems like another line to get wrapped around something (neck, wrist, leg etc) in a pitch and cause some real damage. I have rescued people with their mainsheet wrapped around their body and completely incapacitated (Hobie 16/20 North Americans).

But on the other hand...
At the Tiger Worlds in Santa Barbara, we rescued around 10 crews that were separated from boats over the course of racing. In 25 kts a boat on its side will travel waaaay faster than a person can swim. We would mostly spot the boat over from mid course and then head upwind to scoop the skipper and crew. It's very difficult to see people in the water in those conditions, even though we knew they were not far from our position. Oftentimes, one of the crew would still be with the boat and they would point us in the direction of the man overboard. It was pretty hectic. A teather might have been a good option in this case, but it just seems like a heck of a liability.

I did get several calls from people overboard on the VHF. They would guide me to their position. And pretty much every coast guard and harbor patrol boat has an RDF on board. A VHF in the lifejacket should be mandatory along with a few rocket flairs just in case, but I'm not convinced about the tether yet. Too much stuff to get tangled up in if you need a quick escape.