Instant Kernel Development Environment

"qemu(x86, arm)" + "nfsroot" + "gdb"

You don't have to care about kernel crash.
You don't have to bring a target board on your business trip just for basic usage.
You can monitor internal kernel behavior by using gdb without additional patch of kgdb against vanilla kernel.
You can try several architectures(x86, arm) and also virtualization.
With nfsroot, you can update kernel modules and user applications easily without rebooting system.