The Sensor Controller is used with items from the ccSensors mod. Also called a "Computer Peripheral Block", it provides a central collection point for the remote sensors readings.
To use it, place this block directly next to a Console, and enter this command in the console(Computer Craft Computer) itself:
/ccSensors/console If there are any Sensors that are transmitting on the same frequency as that controller, it'll receive data from those sensors. With the above command, you can obtain readings from those sensors.
Go to ccSensors for information on how to use this with other ccSensors blocks and items.