Ive got a first version of a bootloader working.
Using Bohne's asm serial and aziemer 256 word asm bootloader.
But when i have uploaded a sketch the bootloader is gone.
The attiny84 doesnt have a bootloader section in the fuses to protect it.
So the bootloader has to fix that. But my asm skill are none existing.
Im already happy to incorporate the asm serial.
Looks like the bootloader is still 256 words (512 bytes) as the arduino bootloader is 2048 bytes 
I have mailed the author of the 256 word bootloader if he can help me out.
Or maybe Bohne can help with this.