WhatsMe app allows you to open chat with anyone on WhatsApp without save his/her number on your phone, as we all know that we can't open chat with someone without save the number on your contact but with WhatsMe you can do it with easiest way just by writing the number of your friend or anyone you want and click open chat and a conversation with the number you wrote will appear and you can send message.
Also WhatsMe allows you to open conversation with yourself and as we also know that WhatsApp doesn't allow to open chat with yourself in WhatsApp but you can do it with WhatsMe.
WhatsMe is easy to use because it's not complicated , has just textbox to write the number and button to open the chat with the number you wrote.