IP/GSM is a more modern way of monitoring a fire alarm panel. Because code requires 2 paths for monitoring, a primary and secondary, the IP/GSM devices allow for such capability by having the ability to send and receive signals over internet, or cellular. These devices can work with fire panels with out any configuration in the panel, as it will automatically answer any incoming calls to the communicator.
The system is simple. Most IP/GSM devices will send signals based on contact closure (FACP relays), older City Tie devices, or the most preferred method - Contact ID from the panel's phone lines. Which ever method is used, the signal will attempt to be sent over the internet, but in the event it cannot be sent out, it will go over the cellular network instead. As long as the cellular signal is reliable and the internet connection can be hooked up, it's easy to install the IP/GSM communicator right next to the panel to save time and money.
Similarly to POTS Monitoring, Contact ID signals can be sent out, and a fire department could track each and every device in alarm if they wish to. A SIM card from a cellular carrier must be put in place in order to properly use the communicator.