This is the simplest way to open a WhatsApp conversation without having to save the number into your contact list. It doesn't require any other WhatsApp application to do it.

This simple app works on any Android device, even if you don't have the official WhatsApp application installed.

The program will scan your call history in order to identify the numbers you have saved in your phone, this allows you to choose the ones you want to connect with. You will also be able to send pictures, documents, audio files, etc.

The advantage of this app is that you don't need to save any of these numbers in your phone in order to open a conversation with them.