I use a PDA that has the Polar PE Manager software on it, with my class lists downloaded on it. I use it in conjunction with the Polar Heart Rate Monitors. Both the watches and the PDA have a infered port on them so I can quickly send the information from the watches to the PDA and show the students their heart rates.
I have a PDA and I use it for assessments. It is a lot easier to assess and then record it right on my PDA, rather than write it down on paper than transfer it to my computer. I can record the grades on my PDA and I have software that allows me to also use it and make changes on my computer. I would recommend it!