Just a word of caution. Installing generic smokes is no prob but installing a full blown (yet small) FA system opens a whole bucket of (liability) worms. If you're not licensed as a FA installer you would do well to check with your liability carrier to see if you're covered. My business insurance is thru Safeco and there is a clause that specifically says "no Burglar alarm or Fire Alarm installation".
Having said that ... think about wireless. Ademco, Inovonics ITI and a few more all make wireless systems that work well. The only hardwires you need are the horns and pulls, the smokes are wireless (and I heard, but haven't yet used, that there are wireless pull stations).
