instead you go for RTLinux i suggest you go for VxWorks . Make an application for Routers Tcp/Ip or others Vx Works has a great market . I think you ve alreadsy go thru UCOS II (thru Labrosee) .
if u r not interested in networks build an interuppt handling in Vx works or
if u want to go for hardware also go design RTOS for any UC 8051 any other
see ya best of luck