OK --- so the typical smoke alarm isn't all that visually obtrusive --- but it is when compared to Kidde's Silhouette smoke alarm! 

This low-profile smoke alarm protrudes less than half an inch from the ceiling, blending in much more nicely than a traditionally shaped smoke alarm.  Furthermore, it uses a rechargeable battery that will last the life of the alarm!  No more changing the batteries when the alarm starts beeping!