You can't split baseband (composite) video or component video this way because the video inputs (sinks) are relatively low impedance and the overall signal gets pulled down too much (making the picture darker.)
But you can usually split analog audio with a Y cable or connector. Analog audio inputs are usually very high impendence so the signal is not attenuated much by splitting. There are two (rare) problems that you might run into when splitting audio to multiple sinks: 1) We have seen some miss-behaved equipment put noise out on the inputs when those inputs are not selected or when the unit is in standby. 2) With analog audio connections, the more devices you hook it up to, the more chance there is of a ground loop. This will cause 60 cycle hum on your audio connections. Just make sure all your equipment is connected to the same AC breaker and a common ground.
