PDQaltair's comments on the shock absorption issue must not be dismissed.
As a climber myself, I am shocked that the basic physics of a fall on a static line are not appropriately addressed with current tethers. My current home-made tether includes a screamer, but there is an alternative to the screamer...
In europe there is a climbing style called
that involves climbing a mix of rope, and re-bar rungs that resemble a ladder. The climber ascends the ladder/rock mix using what looks exactly like a double yacht tether. An important difference between this style and conventional rock climbing is that there is NO ROPE. The climber climbs hundreds of feet using only a double yacht tether tied to his harness. If he falls the tether and harness catch him, and of course, all the tethers have shock absorbers built in. Many use screamers, but KONG makes a reusable shock absorber. The shock absorber uses friction going through a plate. Sailors may recognize the plate as a familiar concept similar to the Wichard Gybe'n'easy.
Kong KISA:KONG - Carabiners, Climbing Gear & Safety Equipment (.Doc.408)
Via Ferata Tether: (This would work GREAT as a yacht tether)