You know you have to pack your regulator or hiking boots for that destination, or the trip may not be alot of fun (or worse, you may have to use rental gear.) But one thing that people sometimes forget is their health and there are things you should be ready for - if you are active there is always the chance of an unforeseen emergency.
1. Make sure that you have an adequate supply of any medications that you take, and then take a bit more. If you are delayed somewhere in your travels you do not want to run out of medicines that you need.
2. If you have a medical condition(s) and you are traveling somewhere where they do not speak your language , try to find a way to have your conditions, allergies and medications translated and have it on a card that is readily available. In the event of an emergency being able to provide such information easily can be very important. Let's put it this way, if you are cut badly, do you want someone to give you a shot of penicillan when you are highly allergic to it? Along the same lines, make sure to receive medical clearance to engage in the activity you plan to do - certain medical conditions and activities do not mix.
3. If you are a diver, get DAN Insurance. If you are experienced diver, you probably already have it. If not, check out DAN's site here. It is something that you hope to never need, but if you are a diver and get injured, it is worth every penny. Better yet, DAN does alot of research into safe diving so your premiums are put to good use. (They now also offer seperate travel insurance. Again something you do not want to actually have to use.)
4. Learn CPR, even if you don't travel. Certain parts of the United States require people to be trained in CPR prior to being able to get a driver's license. These areas have shown a substantially higher survival rate for heart attack victims. Many communties offer training for free or a nominal rate.
5. Research/learn first aid. Whatever activity you engage in has certain risks associated with it and injuries which are more "common" - divers and beach goers have a better chance of being stung by a stingray than a mountain climber does (though you may both be subject to overheating). Learn how to treat the injuries you may encounter, and carry a first aid kit to treat the injuries.
Hopefully you will find time to become prepared a bit more for your travelling as discussed above. And hopefully you never have to use it.
Safe and fun travel everyone....