I am doing the exact same thing.
Most likely your local (fire) code authority (AHJ) will specify that you need to have your fire sprinkler flow alarm integrated with your smoke detectors (but not your CO detectors, because that makes sense -not-). And all of those have to report to a UL certified central dispatch station. Some AHJ's (very small towns) will allow direct calls to the authorities but beware of false alarm fines. You will thus need an alarm panel capable of integrating your hard wired alarms.
The problem is that each manufacturer has different ways of interconnecting hard wired alarms. You cannot mix and match brands or even types. If it is a high voltage smoke detector with a third wire, you most likely cannot just jigger something on the third wire and expect it to work (also, not UL approved means it won't be accepted by your AHJ). Some high voltage system manufacturers MAY sell a relay that you can integrate into your low voltage alarm system, more modern systems actually do some sort of communication on the third wire. Also, most AHJ's will require that if one alarm goes off, all of them need to go off so if your fire sprinkler system goes, all alarms have to go so there needs to be communication in both directions.
I have opted to go for a Honeywell Vista system with System Sensor low voltage CO/Smoke/Heat alarms (COSMO2W). It is probably the easiest way to go. You then can integrate the fire sprinkler detector as a hard wired zone into your panel as another fire zone and all alarms will sound at the same time. Remember to use the super-expensive fire-rated wires as regular good-quality wire although physically the same material and on-paper has the same melting properties, is not the right color)