Have recently come across the Livestrong Calorie Tracker App for the iPhone via this months UK edition of Wired
Admittedly, the GUI isn’t perfect and it’s started to intermittently crash when used in the last couple of days but as a way of tracking your calorific input it’s been pretty good so far.
I think it has much to offer regarding wider health benefits and applications in QOL improvement and dietary management as it’s pretty easy to use.