Here is a simple Electronic Switch which can be operated by any Magnetic Field.  It can serve purpose of REED Switch with little modification using a relay because it can not directly drive electrical loads as their output drive capabilities are very small around 10 to 20mA. You can also use  transistor as current amplifier.
For the simplicity of the circuit I have used few components. In this circuit I have used Hall Effect Sensor, one LED and a 9 Volt battery. 5 Volt is enough for the circuit to operate. In market you will find two types of Hall Effect Sensor, Latching and Non-latching Sensors. In Latching type sensor, output state does not change even when you pull magnet away. In this project I have used Latched Hall Effect Sensor US1881. A electromagnet can also be used to control the circuit from a remote point.
Magnetic Switch                                                                                                                                                                                                                                                 Picture of Magnetic Switch
Application of Hall effect Sensor

  • Speedometer
  • Space Technology
  • Proximity detector
  • Brush-less DC Motor Communication

View video of our experiment