GESTION DE QUEUE PAR SMS

Objective: create a queue system managed by an Android smartphone.
The smartphone will send sms to subscriber based on status of the queue.

IMPORTANT
The smartphone running the application will be sending sms through the cellular network (GSM/3G), so there is no connection to internet or any server what so ever (no back end). The sms will be charged on the SIM card inserted in the smartphone. We are talking about standard sms sent by the modem in the phone.

This is for private use, a doctor who is a family member asked me to create something for him.

Background:
To handle the queue of customers waiting in an administration or any office, systems that print tickets have been developed.
Typically, when you arrive at the place, you will see a ticket dispenser from which you collect your number. The ticket dispenser can be a simple roller or can be more advanced with a console offering several possibilities from which the user have to choose and then a ticket will be printed.

Once you take your number, you will monitor the queue by checking the screen displaying the current number being served. When a customer is done, the office employee will press a button to call the next customer, the number will be updated at the screen (a sound notification is usually added and the display can also indicate the counter number in case there are several).

Problem: in some cases, the queue can be very long and the waiting time can reach several hours.
Instead of waiting in the waiting room, the customers may be tempted to go outside to avoid wasting time and make use of the time to do something else (having coffee, shopping, going back home, meeting friends…).
But at the same time they don´t want to miss their turn if they happen to be away too long. So, they will face a dilemma: “Should I stay or should I go?”

General idea: customer should be able to monitor remotely the progress of the queue (number being currently served) in order not to miss his turn when it comes.

How:
We could imagine a web page displaying in real time the status of the queue where the user can log, but for the moment we don´t want to consider this option as not all users have a Smartphone with internet access.
Furthermore this requires action from user who needs to frequently check.

Chosen option: give the possibility to the customer to be informed in real time by sms when a new user is being served. The sms is sent by the smartphone running the application.

Current solutions: advanced queuing systems already have this feature but those solutions are more tailored for big organizations and would be too costly for a small doctor cabinet (those solutions rely on a web server connected to a sms server, plus HW equipment console).

Our goal is to have this system running on an android smartphone .

Hardware should consist of the following elements:
- An android smartphone + SIM card
- An android tablet (which will acts a display)
- In option a Bluetooth printer

How does works:
1- The patient c arrives at the reception, he will be given a number, let´s say number 7. We call this customer c7
2- The patient being currently examined is number 1 (information displayed on a screen), current turn is t1
3- This means that there are 6 people before patient c7.

Patient c7 is offered the possibility to get SMS when the queue is moving: he will have to choose for which turns he wants to be notified. Example, he wants to be notified for turns {2, 5, 6}.
The reception personal will enter the following information in the system (which consists of a smartphone with the android app):

Customer will have the following attributes
1- Customer queue number: c7
2- Desired sms: {2,5,6}
3- Mobile Phone number: [Téléphone visible pour les membres Pro]
4- Name: optional

The queue will have the following attributes
1- Number currently being served: let’s call it t1
2- For each turn, there should be a list of the customers (with their phone numbers) who have subscribed to that turn.
3- Possible actions on the queue: can be incremented, decremented, reset