BeOS (Haiku's emulant) and QNX were close cousins and competitors at that time, both staking out territory in the high-performance RTOS space. IIRC QNX offered

BeOS (Haiku's emulant) and QNX were close cousins and competitors at that time, both staking out territory in the high-performance RTOS space. IIRC QNX offered hard realtime guarantees that BeOS did not, but was more limited in what it supported. I gather it was more successful in scaling down to embedded devices, too; BeIA pulled a number of tricks to get its image sizes down, but was still targeting pretty fully-featured multimedia-capable devices.