Not all all. Apple can make firmware so that it only works on this particular phone, and they can modify future phones to prevent this method altogether.
You know this how?
For example I have a bleu cheese salad that I make a couple of times a week. Figure out the ingredients and weigh them (I bought a cheap food scale at NewEgg) and it's not that hard. It also has the side effect of making you aware of where your calories are coming from.
I guess I'm a little surprised that someone who is patient enough to actually cook from scratch would then be too lazy to weigh a few items.
"Floggings will continue until morale improves." -- anonymous flyer being distributed at Exxon USA