I also have switches mounted on my steering wheel, but I am using >the Cadent Technologies turn signal module. It auto cancels after 15 seconds, but the countdown clock will reset itself whenever you apply and then release the brakes. This is a very useful feature when stuck at a busy intersection. It also has an option to rapidly flash your brake lights three times upon initial application. I am runnning my roll bar mounted third brake light to that circuit and it really seems to get the attention of the latte drinking, cell phone using SUV drivers here in Seattle.
http://home.comcast.net/~cobar/images/dash.jpg
-John