You may want to wait until the packing list appears in your portal in case anything changes, but on the recommended list last year was - wrist watch (conservative and in good taste).
Within that guideline - I recommend an inexpensive watch with the following:
- Predominately dark color -black, dark gray, olive drab, etc.
- Digital with light button - much easier to read quickly/accurately and in the dark
- Waterproof/resistant - doesn't need to be rated to 20,000 leagues under the sea. Just so you don't have to worry about it if it's submerged in shallow water or in heavy rain etc.
- At least 1 alarm so you can wake up before the cadre wakes you up (you won't have enough time to get ready if you don't get up early). Additional alarms can be useful.
- Rubber/Plastic band. Much easier to keep clean.
- Casio and Timex make several different models with these features between $15 - 50.