That was the idea of ​​a startup.

The idea is to create a sarvis "My phone book"
Actually the reason for which this idea came to mind, I needed a phone number of a friend. And this number was in my house on a piece of paper. Fortunately, the spouse was at home and dictated a number to me.
Actually now to the project itself.
The essence of the project is to make it your own husband to create your phone book, and to have access to it all the time.
+ the ability to synchronize with the phone
+ You probably had to call your friends and get to know the phone number of some common friends, or the phone number of a friend and so on. mn
To solve this problem, you can give access to your friends to your phone book.
Sometimes it happens that just fussing and forgetting the phone at home, but you need to call someone. And in this case this service will help.
Alternatively, you can still think of how to further develop this service.

Yes, there is nothing particularly conceptually new, and there is no difficulty in developing this service.