Behavioral Economics is "about helping people to avoid making a decision that they themselves would consider a mistake" and "…the most interesting and innovative tools are those that make it easier for people to do what they already want to do — to realize their own good intentions."
Studying behavioral economics helps us understand the gap between intention and action. Our intention can be to eat more healthily, to exercise more, to save more money, to be nicer to people - and the learnings and tools of behavioral economics help us stick to this plan. It helps us stick to something, because it understands that we are highly influenced by context of our decision-making; and it helps us because it offers a model for this decision making that enriches economic models with human psychology.
And that's where digital products, from running trackers to commerce websites, fit in.
Have a look at this article about the misconceptions about behavioral economics.