Usually I just use my normal wristwatch and place it on my exam table for each 3 hours session. This year, I used a digital watch too with a stop reset timer for the AM questions, so both to help with time mangement.
It was helpful to keep me from spending too much time on one question. Caved in and got one a week before the exam.
Anybody else used a digital stop/go counter? I had to manually de-beep mine.