Here is our student payload box.  We tried to make it as light as possible since there will be as many of these as possible on one balloon.  We are trying to keep the balloons we are tracking down to 1 or 2.  We use a Hobo data logger to record temperature, a Sipix stylecam snap for pictures, an adjustable timing circuit for controlling the frequency of taking pictures, a battery powered heating circuit, and two toggle switches to turn the timing circuit and heaters on once your ready for launch.