Wireless. The device is integral vs. a wired detection circuit back to a transmitter. Honeywell and GE offer RF heat detectors (although limited to 135 degrees for listing/operation purposes). The units are typically tampered (supervise removal) and anything off normal is reported (LB) and a missed check in would generate a trouble. In the case of a wired heat back to a transmitter, there's a lot of things that could be done and not report back to a CS, but the largest offender is removing a defective device and wiring the loop back to keep the panel happy, happens WAY too often. An alarm vendor that is a town over from you has a glass case with beautifully painted heat detectors and the piece d' resistance is heats and smokes that were "popcorned" by a ceiling/sheetrock contractor.
As far as separate transmitters connected to a wired detector, GE units have a resistor but can't remember if they're listed off the top of my head. Honeywell has a commercial fire listed transmitter with EOLR. Cable length is still limited.
Again, if you're wiring the device, once there's an expander in the field involved or a home run back to the panel, surge suppression is mandated if the cable leaves the building.If you connect to an expander in the field, especially with a M1, a missing or lost expander will be a fire alarm reported. Experienced that on a job before, so that's why I've gotten in the habit of pulling enough copper and trying to get back to the panel wherever possible.