Really nice idea, especially for the bar-code. As other comments mentioned that some similar apps have been already created, from my perspective, this good idea still does not get that popular because most of apps ask people to insert the food information one by one themselves. Convenience is really a crucial element. If scanning receipts can work, it defiantly will help. Look forward to the success of your idea.
There's so much to like about this idea and hope to see it growing till the end. Although it is a really big challenge about how to support people's needs and deepen their experience in the end-of-life time, it is still an inspiring step. Look forward to seeing it available and common as a global task sooner or later.