Which of the following is an example of a financial service?

The example of a financial service is best represented by debit cards. Debit cards are payment instruments that allow consumers to access their bank accounts electronically to make purchases or withdraw cash. They facilitate financial transactions by providing a direct link to a user's checking account, enabling instantaneous payment without the need for cash. This ease of use makes debit cards an essential component of modern financial services, as they streamline purchasing processes and enhance convenience for both consumers and businesses.

In contrast, the other options presented are not financial services. Interactive assignments via WebCT pertain to educational technology, wireless orders from waiters to kitchens relate to restaurant operations, and online patient-monitoring systems focus on healthcare management. These elements may involve technology and operational efficiency, but none fit the definition of a financial service like debit cards do, which directly deal with financial transactions and consumer banking.