Wireless commercial fire alarm systems

I had another person ask me if there is such a thing as wireless fire alarm systems.  We may be the only company installing them, but YES they are real.  We've been working with these systems for almost 10 years now.  They are not usually an option for new construction projects, because the material costs are more than hard-wired systems.  But for projects where excessive labor costs, maintaining occupancy, working above manufacturing machinery, keeping historical aesthetics, or other special conditions exist, they can be a better solution.  Wireless device (any kind) talk to each other and the control panel through radio frequency (RF) signals.  Advances in the products have allowed these systems to sense low battery, dirty detectors, unauthorized removal, and other issues that in the past made them unreliable.