Extensible point-of-sale platforms and associated methods

1. A computer-implemented method for an extensible point-of-sale device, comprising:

registering, with an operating system on the point-of-sale device, a third-party application to be notified of a transaction change on the point-of-sale device;

displaying a user interface to a user during a purchase transaction on a display of the point-of-sale device using one of a register module and a payment module;

receiving the transaction change via the user interface of the point-of-sale device;

broadcasting the transaction change to a set of registered applications, on the point-of-sale device, that includes the third-party application; and

taking an action that modifies the purchase transaction using the third-party application in response to the broadcasting;

wherein the set of registered applications are executed on the point-of-sale device; and

wherein the set of registered applications share resources on the point-of-sale device.

2. The computer-implemented method for an extensible point-of-sale device of claim 1 , wherein:

the action is inserting an image onto a receipt printed for the purchase transaction by the point-of-sale device.

3. The computer-implemented method for an extensible point-of-sale device of claim 2 , wherein the action of inserting the image onto the receipt comprises:

transmitting the image to a services process on the point-of-sale device from the third-party application;

adding the image to the receipt using the services process; and

printing the receipt for the purchase transaction using the services process.

4. The computer-implemented method for an extensible point-of-sale device of claim 1 , wherein:

the action is inserting a text string onto a receipt printed for the purchase transaction by the point-of-sale device.

5. The computer-implemented method for an extensible point-of-sale device of claim 1 , wherein:

the action is displaying information on the display of the point-of-sale device.

6. The computer-implemented method for an extensible point-of-sale device of claim 5 , further comprising:

generating the information to display on the point-of-sale device using the third-party application; and

displaying the information on an area of the display along with the user interface.

7. The computer-implemented method for an extensible point-of-sale device of claim 6 , wherein:

the third-party application displays the information on the area of the display independently of the register module and the payment module; and

one of the register module or the payment module concurrently displays transaction data along with the information on the display.

8. The computer-implemented method for an extensible point-of-sale device of claim 1 , wherein:

the action is inserting a user interface element on a payment window display screen of the user interface.

9. The computer-implemented method for an extensible point-of-sale device of claim 8 , wherein:

the third-party application displays the user interface element on the display; and

the payment module concurrently displays a payment window on the display along with the user interface element.

10. The computer-implemented method for an extensible point-of-sale device of claim 9 , wherein:

the user interface element initiates a method of payment provided by the third-party application.

11. An extensible point-of-sale device, comprising:

a POS processing service that registers a third-party application to be notified of a transaction change on the point-of-sale device;

a display that displays a user interface to a user during a purchase transaction; and

a register module that receives the transaction change involving the purchase transaction via the user interface of the point-of-sale device;

wherein the third-party application is configured to take an action to modify the purchase transaction in response to a trigger; and

wherein the POS processing service is configured to provide the trigger via a broadcast of the transaction change to a set of registered applications that includes the third-party application.

12. The extensible point-of-sale device of claim 11 , further comprising:

a printer that prints a receipt for the purchase transaction with an added image using the POS processing service on the point-of-sale device;

wherein the action is transmitting the image to the POS processing service from the third-party application;

wherein the transaction change generates a printing receipt event to initiate a printing process; and

wherein the trigger is the printing receipt event.

13. The extensible point-of-sale device of claim 11 , further comprising:

a printer that prints a receipt for the purchase transaction with an added text string using the POS processing service on the point-of-sale device;

wherein the action is transmitting the text string to the POS processing service from the third-party application;

wherein the transaction change generates a printing receipt event to initiate a printing process; and

wherein the trigger is the printing receipt event.

14. The extensible point-of-sale device of claim 11 , wherein:

the action is generating information to display on the display; and

the information is displayed on an area of the display along with the user interface.

15. The extensible point-of-sale device of claim 11 , further comprising:

a network connection; and

a local database that stores the transaction change in a queue;

wherein the point-of-sale device is configured to upload the transaction change from the queue via the network connection when the point-of-sale device is able to communicate with a server.