Some other questions about HUDs and how they work got me thinking. Military aircraft have had reflector sights since before WWII, and full HUDs since the mid-70s. The very same display layout, sans targeting recticles, is fairly familiar to pilots of glass-cockpit aircraft, the primary difference being the representation of the artificial horizon (which, because the display is not a HUD and so not transparent, uses the blue/brown background from the analog instrument).
True HUD systems are starting to make their way into commercial airliners, and the technology is even seen in various cars (primarily luxury brands) as a situational awareness tool. So the question is, what types of reflector-sight flight display systems are available for light singles? I would assume a glass cockpit is a prerequisite to generate the digital display, but given that concession, it seems fairly straightforward to have a monochrome version of the PFD projected onto a glass plate instead of or in addition to the display on the LCD monitor. Has anyone marketed this? Are there disadvantages of having a HUD in a GA aircraft that I'm not thinking about? This sounds like a natural next step now that even entry-level LSAs are foregoing the traditional analog 6-pack for glass displays.