Your idea for an app that combines the features of a personal diary, location-based shopping deals, event planning, and real-time friend tracking sounds innovative and multifunctional. Let's break down each feature and discuss how they could work together:

**1. Diary/Appointment Manager**: An app that allows users to plan their schedules in advance is incredibly useful for keeping track of appointments, birthdays, and other important dates. The ability to send notifications as an appointment approaches ensures that users never miss a scheduled event.

**2. Location-Based Shopping Deals**: Integrating a feature that helps users find nearby stores with the best deals can save time and money. This is especially useful for people who are looking for a convenient shopping experience.

**3. Event Planning**: Coordinating with friends and family can be challenging, but an in-app feature that streamlines the process makes planning get-togethers much more manageable. If the app automatically shares event details with everyone involved, it reduces the need for multiple messages or calls to finalize plans.

**4. Real-Time Friend Tracking**: Allowing users to see their friends' or family members' estimated time of arrival (ETA) and their proximity can be helpful in various scenarios, such as meeting at a cafe or restaurant. Offering speech options to relay this information is an added convenience, as users can get updates without needing to look at their devices constantly.

Combining all these features into a single app creates a versatile and efficient tool that caters to multiple user needs. It could potentially become a popular choice for people seeking an all-in-one solution to manage their daily tasks, shopping, and social life. If executed well, the app could streamline many aspects of users' lives and enhance their overall experience.