@Dandy
I made two suggestions a while back.
1. The first was to use it for CNC machine control for manufacturing stuff (whether that's in a factory, or someone's garage). CNC machine control requires very precise timing and simutaneous control of multiple stepper motors. I've heard of trouble when using PCs for this task, where the OS mucks up the timing and causes manufacturing defects. This is with the CNC machine's stepper motors being controlled by bitbanging an old fashioned parallel port. Xena/Xorro would have a few advantages. Firstly, it should be able to drive multiple stepper motors simultaneously than a parallel port. Secondly, the CPU has very very low latency when sending data/commands (no drivers, USB controllers/buses or other things in the way). Finally, AmigaOS' multitasking should be able to meet the hard realtime requirements, even though it isn't a "realtime multitasking" OS.
2. The other suggestion that I had was to use it as a "super debug port." One problem that I have with debugging drivers, is that I have to output debug data to the serial port (if the graphics driver crashes, then you won't be able to see/save it to disk). The serial port is painfully slow when there's a lot of debug info. My idea would be to stream the debug data via Xena at high speed, and have it write that data to log files on a SD-card (a high-speed one, like you would use in a camera). After a crash, the debug data could be retrieved and read directly from the SD-card via Xena. This would both speed up the debugging, and eliminate the need for a serial cable and second PC.
Why not stream it to disk via the OS? Well, an OS crash could prevent the (often critical) last few bytes from making it onto the disk. With Xena handling the writes, every last byte will safely end up on the SD-card.
Why haven't I done either of these? I simply don't have the time right now.
Hans