It seems that vibration is a very common element in modern gaming. Lots of joysticks have it built in to give the player a more immersive experience. For example a bomb explodes close to you and you can feel it in the joystick, you get shot and you feel that too. The Virtual Impact Suit takes it to the next level, you would literally feel the bullet hit you in the chest!
Code and schematics are available on the site.

” The PC Virtual Impact Suit takes in-game bullet hit events into real life physical impacts on player’s body. It currently supports the popular Half-Life 3D first-person-shooter game, and connects to the PC via a USB port.

The electromechanical suit is powered by low voltage.

For those who would like to build their own Half Life Impact Suit system, the following is being provided as free, and for non-commercial use only. “