With iOS 10 it is easy to access recent chats and it is done with a widget. You must slide from the center screen of the iPhone to the right, go down to "Edit" and there Add widgets> More widgets> Recent chats. This way you will have direct access to the last conversations. Comfortable and simple at the same time.
Also from iOS 10 you can dictate your messages to Siri without having to open the application . Tell him that you want to send a message to any contact using the command "Send a WhatsApp to ..." and tell him clearly what you want. She will read it to you before sending it and if everything is correct, tell her that you want to send it. Easy when you can not use your fingers. I was recently with a bandaged arm and Siri helped me a lot in this aspect.