thanks for the links!
1st link: i hate soldering, as my chubby hands always seem to break something

2nd link: flash diffusor is cool, will probably build one soon.
3rd link: soldering again, yuck
4th link: solid gold, thanks

5th link: not too bad as well, much to read there, but for now i will experiment with my fiber optics
i found me a longer cable, thinner and MUCH longer, i think it is 20 meters or longer. i still havent assembled anything sophisticated, i just did this small test:
turn on camera, pop up flash, set flash to "always".
load chdk, load intervalometer script, set to "shoot once every 10 seconds"
take one end of the optical cable, somehow "lean" it into the flash of the camera (taping would be better, but i just made this simple test)
take the other end of the cable, go to another room with it, or leave the flat if your flat isnt big enough (well you can also stay in the same room, but then the test isnt really proving that the cable was used)
hold the end to the slave flash's "trigger diode" - now watch a burst of flash triggered every 10 seconds. i didnt even have to hold it directly above/in front the diode, it was even working holding it like 5 cms away from it, just pointing it in the general direction.
conclusion:
- it doesnt really matter how long the cable is, my guess is that you can even use 50 m or longer. now you may ask: what would i need that for? well for example you are shooting using zoom, and you want to light your subject - there is NO way the built-in flash will reach the subject, so you either need one of those radio controlled pocketwizards (which wont work with our cheap cams) or a pc cord (which also doesnt work with our cheap cams, plus they come in like 5 meter long - too short!) or the optical fiber cable. also you sometimes need a long cable when for example you are shooting someone with a wide lens and the flash is behind the subject - where to hide the cable? having a long cable allows you to go "outside of your cameras radius", if you catch my drift.
- since i just made a short test with "holding in the general direction of the trigger", i can safely assume that once i build a construction that allows me to attach the cable to both camera and flash securely, tightly & "unbreakable", there is no way the flash will NOT trigger, also my construction will not have to break anything in the shell of the flash or my cameras body (since i dont have to affix the cable directly IN the camera's flash or directly ONTO the trigger of the external flash)
- it is cheap and reliable (just checked for prices of optical fibers - like 5 bucks for 10 meters on ebay, which will be sufficient i guess)
- using this construction will put an end to the firing of MY external flash because someone elses camera is using flash.
- using this construction you can make sure your subject is lighted by the external slave flash and the ambience only, not by your camera's flash.
will post video + pics here soon i guess.
by the way: after some research i found something that MIGHT be of use for us cheapskates:
radiopoppers. These "transfer" the optical signals from the expensive wireless TTL flash/cams via radio signals over a great distance. here's the catch: 180 $ each and also the
radiopopper jr. (which will be the gadget helping us) is not released yet, but are supposed to weigh in 25$ only (the normal radiopoppers most definitly only work with expensive lighting gear/cameras). here's an article about the "normal radiopoppers":
Strobist: RadioPoppers: Not Just For Wireless TTL