Retailers such as Target and Amazon are embracing mobile applications to help consumers save money and time with features like digital wallets and augmented reality. When used strategically, apps can streamline in-store trips and online purchases, but shoppers could also find that convenience comes with a risk: impulsive decisions and overspending.

"Now shopping can be anytime, anywhere, multiple times a day, which is great for customers who value convenience," said Casey Taylor, a partner in the Atlanta office of Bain and Company, a management consulting firm. "But for customers on a budget,...