some questions regarding bootloader on mega128

Hi alltogether,

I have some questions regarding the bootloader on the mega128.

Is it possible to jump to the bootloader section from the application
section?
E.g. 	    
	if (command == ENTER_BOOTLOADER)
		asm volatile("jmp 0xFE00");

Or must I initiate a reset, possibly by triggering a watchdog timeout?
(I have no portpin connected to reset nor the isp pins, and the pcb is
in production.)

Does a watchdog reset jump to 0x0 or to the bootloader-startadress?

Perhaps there is something "ready to use" using protocols included in
avrdude?

Currently I'm investigating Jaroslaw Karwiks derivate of the AVR109
app.note, and it seems to 
 follow the same protocol as the cheap serial avr programmer (name
forgotten).

TIA
/Marc