To implement this system, you'll require a minimum of two mobile phones. One phone should have the counter app installed and be positioned near the production or assembly line. The second phone should have the manager app, and the manager should be in close proximity to monitor the results and receive alarms.
For scalability, you can easily increase the number of counter apps if you have multiple production or assembly lines. Similarly, you can expand the number of manager apps if you have multiple managers overseeing different aspects of the process.