The transmitter sends a wireless redstone signal when powered. Right - click on it to open up a GUI. Type in the name of the channel you would like to send your signal through.
This is what will receive the redstone signal from your transmitter. Right - click it to open up a GUI. Type in the same channel as you have typed in your transmitter. Power your transeiver and your receiver will receive the signal.
The remote is technically a portable transeiver. Just set up a receiver (set the channel) then right click the receiver with your remote. The remote is now linked to it. Right click with the remote anywhere in the minecraft world and the receiver will receive it.
You can also do a quick "channel swap" by right clicking any Transmitter this will automatically change the channel for you.
Item Motion DetectorEdit
This is rather simple. If the detector detects an item anywhere in its range, it will send out a redstone signal. Its range no longer depends on what it is placed on (as of 1.2.7). If it is placed on anything its range is only 3 blocks away this gose for all blocks and was proven in practice by DemonicJoker.
Mob Motion DetectorEdit
This does the same thing as the Item Motion Detector though it detects mobs (other than the player).
Player Motion DetectorEdit
This does the same thing as the Item Motion Detector though it detects players.
Signal Lights (Control Lights)Edit
This is simply a button-sized block that emits light when powered, They can be coloured to match any given color in the game by using dye.