The application allows you to remotely connect via Bluetooth to any device using the Modbus RTU protocol in master mode. To do this, you still need an adapter, which is easy to implement using Arduino and any other controller. The adapter receives the master request from the phone as a byte array. The response from the slave device is converted into a HEX string and sent back to the smartphone.
Using this tool, you can connect to any device using the Modbus protocol and view the contents of its registers without using a laptop for visualization.