As
@DonManfred says, it is virtually impossible to automate Whats Apps and will lead to frustration by the user.
My suggestion would be to use MQTT, such as in this
link, and with some clever programming you could achieve this quiet easily. To make it pretty you could use (
link)
Now, If I had anything to do with it, I would have my jRDC2 server running hooked up to a MySQL Database to fetch all my data as required. Then I would have a MQTT Server running that will handle all my messaging and with some clever programming (a few cups of coffee in between) I can send a MQTT message to my B4J back end - that would look at what I am asking, request the information from the jRDC2 Server and return it via MQTT.
Now the catch is here. MQTT is a publish/subscribe system, so if you send the MQTT message without a few tricks, then everyone will receive it. EISH !! All you need to do is make sure your requesting app publishes the message to the server only. In this message that you are sending to the server, (use jSON) include the sending user name to the server, which you then use to send the message back to the user who sent it, by publishing to that name only.
My apologies if this is a disruptive spanner in the works reply - but it works for me.