I've been using the Bethwaite key&ball setup on my traps for over a year now. Advantages are there is no hook on the trap harness to snag rigging or puncture decks/hulls (happened twice in 6 months with a standard hook system on my Tornado) and the key/ball system is noticeably lighter over the standard stainless hook & rings. Go with the carbon/kevlar option on the key spreader...there were problems with the plastic ones in the past.

For emerg knife, I found a titanium blade called "River Knife" for $45 from MEC (that's Mountain Equipement Coop...Canada's answer to REI here in the States). I have also seen a type of blade called a bear claw that search & rescue folks wear. It has a short, curved serrated blade that is held in such a way as to reduce accidental hand cuts etc.

What ever type you go with, make sure you can easily attach it within reach by either hand onto your life jacket or leg. When you need it, there's no telling where on/under the boat you'll be.

Mike.