Firmware, which work only one time.

[ghost]

Hey,
Is possible to do firmware, which work only one time?
Something like that:
if(read_flash_at(FLAG_ADDR) == 0) then
send_keys();
write_flash_at(FLAG_ADDR, 1);
end

What should I know to do it?

Will be nice if I get answer from person, who is practitioner, not theoretician :-)
Regards