Smoke detectors have become an interesting item here in California. As of Jan 2014, the state has banned the 9v battery type only allowing stores to sell the "Long Life" variety, which contain a 10 year battery sealed inside for the life of the detector. Yea, you can still get the 9V replaceable ones on amazon, but not in a sticks and bricks store.
There is not a different type for RVs, but a smoke alar is not a smoke alarm. There are two different technologies, and the difference is important.
Ionization and Photoelectric.
Ionization are cheaper and more prevalent. They cause 95% of all false alarms (like when you boil water of cook bacon). They respond A LITTLE faster (30-60 seconds) than photoelectric to fires with lots of flame and little smoke. But they respond MUCH slower or NOT AT ALL to smoldering high smoke fires!
Photoelectric are a little more expensive, not as prevalent, cause almost no false alarms to cooking (you often see them advertised as "for kitchen"). They respond a little slower to low smoke fires, but much faster to smoldering fires.
There have been many special reports showing how poorly ionization detectors respond compared to photoelectric. A photoelectric may take a couple minutes longer to respond to a low smoke fire, but ionization detectors take 15-20 MINUTES LONGER to respond to a smoldering fire. There have been reports where working ionization detectors did not alarm AT ALL.
I am in the same situation, I will be getting one of the 10 year photoelectric/co detectors for the trailer. About $40 at the store