The controlling unit in building management system automation is a PLC. Every device in an installation is connected to the PLC. When a user wants to interact with a system an operator terminal, which is attached to a cabinet where the PLC is installed, is used. With this solution the user needs to be in front of the cabinet to interact with the system. Alarms do not get the user’s attention until the user checks the operator terminal. Using a solution where the communication with the PLC is done with a wireless interface would mean that the user interact with a system from a wider area. The solution should have the same functionality as today with the extension that the PLC should be able to contact the user if something is wrong in the installation. A PDA is used as a replacement for the operator terminal. This PDA uses two different techniques to communicate with the PLC. Bluetooth is used when the user is in the building and interacts with the system in a similar way to the operator terminals. GSM is used when the PLC needs to get the users attention by sending out alarms. With this solution the PDA can be used for several installations and thereby decrease cost. The project has turned out to be a success. The application that has been developed has improved a user’s interaction with a PLC.