If you look at the book store there are lots of the pocket sized ones. Never used any in particular but I'm sure it would depend on the person. Just browse through it and see if it contains the kind of foods you eat. For example if you're looking into making health on-the-go choices, make sure it contains a fast food section.
Alternatively, you could use www.fitday.com
Many people around here, including me, use it to track our calories. It has just about every food imaginable. If there is something specific you have that they don't (say a certain meal replacement bar or a recipe) you can create a "custom food" where you name it and put in the calories, fat, etc. In addition to keeping track of your calories, its a good way to see your macronutrient ratio. It also gives you nifty weight charts and calories burned during exercises. All kinds of useful stuff.