If you have multiple reservations for car, hotels, etc. you may want to email a copy of those and of your itinerary to yourself. That way, you always have it with you and don't need to look for a paper copy in your bag.
If you plan on using your phone to retrieve that information, be sure you aren't piling up a bunch of roaming charges.
You could also include a list of medication you regularly take, in case you need to purchase some. If your medication is a prescription, consider including the name and number of your physician.