The price of Palm OS handhelds has dropped over the last few years, making them more affordable to enthusiasts who are working within a budget.  If you buy a Palm unit for the specific purpose of using this software, we recommend the following two features: 
 
First, a backlight will be very helpful for the first drive at night.

Second, if you like to log significant amounts of data, make sure you have a decent battery supply, like a rechargeable battery to keep you sane throughout the data logging process.