Lots of concerns.
1) detection without false alarms - are you going to detect smoke? heat? flame? combustion gases? How will information be gathered and processed?
2) impact of alarm on any residents in the trailer. (if you are sleeping and it goes off, do you get 'put out' too?)
3) power consumption, weight, and other related 'off grid and on road' factors.
4) impact of installation on safety by adding additional weak points and complexity to existing systems (turn off relays, more wiring, additional parts and pieces, ...)
5) maintenance and inspection issues
6) dowsing materials handling, storage, and dispersal mechanisms.
7) control and override management and utilization, even logging, adjustments, installation, testing,
8) training and documentation for use, maintenance, and repair.
9) alarm notification and communication - noise? automated telephone call? action verification and authorization?
10) impact on neighbours?
From what I can tell, you can run risks of fire to near zero by doing four simple things. (a) turn off propane at tank, (b) unplug electrical, (c) isolate (disconnect at source) battery, (d) make sure any flamables are properly stored - preferrably nowhere near trailer. The other side of disconnecting is, of course, proper preventive maintenance coupled with periodic inspection and testing.