What are these devices consisting of audio jack and LED(s) OR IR-transistors OR similar looking parts?
One of them has a mono 3.5mm audio jack and two LEDs or similar looking parts - 5mm round transparent things. One side of the enclosure around each "LED" has a sticky tape. If they would be attached to something then the "LED" would face 45 degrees from the surface.
The other has a stereo 2.5 mm audio jack and one dark IR-reciver-like thing in a small round enclosure. The enclosure has two small holes on the other side, but I'm not sure if they are important.
I tried the one with two "LED"-s in a headphone socket but nothing happened.