Intercom systems, most often used within a single building or home, provide a means for immediate communication. Using cell phones as the hardware parts of an intercom system allows the system to cover a much larger range. While most intercom systems have limited range, cell phones are limited only by the strength of the cellular signal and, at times, can provide a worldwide intercom system.
Purchase at least two cell phones with the "push to talk" feature. Sprint/Nextel and Verizon both sell push to talk phones.
Sign up for a calling plan that includes push to talk as a feature. Sprint/Nextel offers this feature as a standard feature while Verizon offers push to talk as a separate add on.
Enter phone numbers of those you wish to be able to instantly connect with to your phone. Push to talk phones can be connected to other phones by either entering the phone numbers as contacts or, as is the case with blackberry phones, using the unique phone serial number.
Test the connection. Using the push to connect or talk button on the phone, select the person with whom you wish to talk from your list and, using the phone as if it were a walkie talkie, test the connection between the phones. As long as the phones are turned on, if the connection is set up properly, you will now be able to mimic an intercom system and have direct access to those in your group.