Like I said earlier you're going to need a good fish finder and GPS, if you're traveling any distance you should also have a radar unit too. I use a Raymarine E 120 and soon will be upgrading to their Wide Screen digital Raymarine unit.
What I like about my E 120 is it's large screen and the detail it shows me of the ocean floor. One of the hardest things about lobster fishing is knowing where they live. You wouldn't fish for calico bass out in the mud so you have to fish for lobsters around rocky areas where they live and hide durning the day. Using my E 120 I can find the rocks and mark them on my GPS at the same time. One hint, don't drop your hoop nets right on top of the rocks, all you'll do is get your nets hooked up on the rocks. They will never lay flat that way and you'll never catch any lobsters. I've had great luck fishing areas outside of large rocky areas.
In your boat you'll need a gaff or boat hook to grab the line from your nets and you're going to need some lights too. I really like the wireless spot lights from Stanley. I have a large one for finding my nets at a distance and a smaller one that I use in the boat for things like re baiting my bait cages and checking to see if a lobster is legal or not. I really like no having to keep the hand held lights plugged in all the time.
I have used both styles for several years now, but the wireless Stanley units are the best I have ever used.