Leica do a monochrome camera too http://en.leica-camera.com/photography/m_system/m_monochrom/ with a similar filter (only necessary to capture colour images) removed. Must be an incredibly small market for these, though...
So this is quite cool. I have to wonder, though, that even if you don't affect light sensitivity, if a higher resolution is going to be very useful. For instance, the glass you put in front of the sensor might affect sharpness in a way that 3x 18 MP won't look better than a Bayer pattern in front of 18 MP. Does anybody know how much light a Bayer filter eats?