Cash register that takes input, does calculations, display updates, and syncs with a database for inventory and pricing. It’s not hard to build a simple one. Make sure you use decimal, not floats, to avoid weird errors.

What would be QNX specific would be making sure the main app is always responsive to user input. That the network, DB, or other things don’t slow it down. That might be done by scheduling dedicated time for both input and the main loop. Non-blocking I/O so main loop can check the progress of other things. Maybe a monitor in there watching for freezes.

If any component freezes, have it restart and get new/updated state. If that works, next version is a two-board, highly-available system with QNX’s networked IPC.