My opening post was too vague and general. I'm planning to use N900 as Wiimote's sensor bar. (Sensor bar is bold name for 12 infrared leds). I have used two candles, but they emits too much visible light when playing/surfing/watching on dark room. And they are not safe when there are children and animals running on the same room. Self made battery+IR-led would work but I'm not handy to make it nice looking. (I almost bought wii wireless sensor bar, but seller didn't know how often battery must be changed).

And I'm Maemo-hacker so I'm looking software solution

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With lirc and endless bash loop I can blink IR-led forever. With one N900 this is enough for wiimote to work (under Ubuntu and open source driver it needs only one led), but it lags/jitters (I think it is because of blinking).

I also test with two N900's side by side, but they are not blinking in same sync, so mouse cursor is continously waving/jumping left to rigth (=not usable).