Currently it is possible to configure new Custom Channel in the journey to send text messages (like Viber/Whats App) but it's not possible to react on customer feedback. Keywords functionality is not supported for Custom Channel in RTM. In Outbound Marketing module such functionality was supported - based on messages with specified keyword that have been send back by customer, it was possible to take an action in the journey. There is no such support in Real Time module. That means that communication with customer is not fully covered. The idea is to extend RTM by adding support for keywords for Custom Channels (as it is already available for SMS).