A new 1.3.1 version of gateway firmware is committed to GitHub which is enabling MQTT subscribe functionality.
Gateway subscribe on topics: /OHS/set/#, particularly parsers following
/group /{#} - index of group {1 .. ALARM_GROUPS}
/state - allowed commands {disarm, arm_home, arm_away}
/sensor - allowed only for Input nodes
/{address} - node address like W:2:I:D:1
/value - float value send to remote node
To describe it better for someone new to MQTT. MQTT is an open OASIS and ISO standard, lightweight, publish-subscribe network protocol that transports messages between devices. The protocol usually runs over TCP/IP. It is designed for connections with remote locations where a "small code footprint" is required or the network bandwidth is limited.
For example:
/OHS/set/group/#/state topics is able to perform disarm, arm_home, arm_away commands for group index specified as #.
/OHS/set/sensor/{address}/value topics is able to receive float number that is then passed to appropriate node address.
Above subscribe and already existing publish functionality allow direct integration with mobile applications, logging platforms for sensor data, or Home Assistant: