Michaela runs a dog-walking business. She has three employees, and she prides herself in maintaining a high level of customer service. She gets about half of her business from last-minute requests. When she receives such a request, she needs to know where her employees are so that she can identify the nearest one who might be able to do the walk. Significantly, she needs this information before she can confirm the walk with the client. Which of the following technologies will help her obtain this information?