* 3 piece Airlock (econolock?)
During the early fermentation, the three piece is nice, to let gas escape rapidly. However, when the fermentation slows, you may want a bubbler-type airlock, so you can see how the fermentation is going. You can count rate of bubble release to see how the fermentation is slowing, and you can observe it like a manometer -- when the fluid level in the bubbler backs up, you know gas has redissolved, and fermentation stopped. Mead can ferment very slowly after an initial burst of fermentation because the environment isn't as optimal for yeast as grape juice is.
Nutrient and energizer are particularly important for mead fermentation. Yeast needs those micro-nutrients to grow healthy. Soon, it will be in a very unforgiving environment -- as sugar decreases, and alcohol increases, and other waste products accumulate. You'll want the yeast healthy from the start ... they only reproduce under aerobic conditions. Once they exhaust the oxygen, only the existing population will continue the ferment. 'Course, some mead aficionados dislike adding any chemical additives, even nutrients, and say they can taste additives.
On that subject, it brings up a who other "holy war" topic. Will you boil your diluted honey, to precipitate trace proteins and sterilize your diluted must, or will you try to retain volatile components by just dissolving the honey in water and starting the ferment? But in that case, what if something else gets hold of your must first? You can get some odd flavors from wild yeasts and bacteria, even if your yeast eventually wins out.
P.S. What do you have to sanitize your equipment?