Spend Stack is a shopping list app that keeps a running total of items including sales tax. The app has a simple user interface that allows users to view and manage multiple shopping lists. The developer's goals in creating the app were to build up their portfolio, help solve the common problem of managing shopping lists, and hook into the iOS community. However, the app did not see much success upon initial release, selling only 4 units. The developer discusses lessons learned around using newer technologies, focusing on usability, marketing and community engagement to help future app projects.