If you have a I Phone or equivialnt, there is a SP app that works superbly. You can do it as you go through your day and it will transfer automatically into your Nutrition page within SP on your computer.
I know this is not low tech, but it is simple and so far, totally accurate and easy to use. I also dowloaded a pedometer app that not only measures your total steps, cals, etc. but will show you a map of your walk.