I've developed a prototype of a food-logging app. Meals can be input using Siri or by typing. There are also a number of UI improvements that could be made over the standard apps (see example below: inputting quantity with a plate diagram instead of manually inputting, say, "13 ounces").
If there are any iOS/backend developers who are interested in collaborating on this, feel free to get in touch. I've just been building this app on the side, but with some help we could get it done much more quickly.
I'm open to other ideas but the basic plan is:
1) Make input of food as seamless as possible (partially done)
2) Create a flexible structure for inputing user-defined response variables (e.g. how you feel after a meal) (partially done)
3) Build out backend (just started)
4) Create some web app visualizations
5) Solve mysteries of science/universe/body
6) (Maybe) Compile a food database
anguspmitchell [at] gmail