John Lee send me this link describing the code that his team is using
for a thread controlling the wiimote vibration.  He thinks it can
also be ported to a xbox controller:

<blockquote>
<a href=http://cs.nyu.edu/~jl205/2007/fall/games/071126/WiimoteRumbleWorker.cs>
http://cs.nyu.edu/~jl205/2007/fall/games/071126/WiimoteRumbleWorker.cs</a>
</blockquote>

This is the wiimote library that they are using:

<blockquote>
<a href=http://blogs.msdn.com/coding4fun/archive/2007/03/14/1879033.aspx>
http://blogs.msdn.com/coding4fun/archive/2007/03/14/1879033.aspx</a>
</blockquote>