The GUI for the app is expected to be a very simple one, allowing
to login with username and password, logout and to set the application as enabled or disabled.

At login the app will send a POST request and receive a token if successful, the token will be stored and used for other api calls. 
At logout the token will be deleted.

Once logged in:

Poll a REST api for data once in a while.
Data includes record_id, phone, message_text
Once some data was received, parse it, store it and send a sms message to the number received in the data.

~Once a day delete any stored data that is over a week old. 

Listen for incoming sms messages.
Once a message has been received, check if the number has been sent a sms message earlier and if so call a REST api with some values from the stored data and the text of the message.
The values to call the api with: record_id, response_text