They allow you to upshift without backing off the throttle.
They are called PK power and work with a power commander 3 and 5 (PCIII / PCV) -also yamaha race ecu and rapid bike ecu...
Cost is $130 shipped - with no rods, I found it better to set it up and grab a rod from Pete (Kaneg) and trim it to suit with a bit of threaded rod if necessary (I have plenty of that if you need it)..!
I can get them to supply the rod as per the pic for $10 extra, but Petes are a better option.
http://www.pk-power.com/quickshifter.php