If you can only control a device by using voice, what is the Task you want your device to perform?

Hi, I Ken Choong. I developing a new project named SarahAssistant.com . The process is like this: You speak to your device -> Your device perform certain task So my question is, what is the "Task" you want the device perform when you speak to your phone? Some of the use case I developing is: - Record your daily expenses - Record your daily to do list - Record your shopping list - Record your audio and make it to a notes So add your use case, what you like to perform by just using your voice?