Quickshifter

[celticbiker]

There is a micro pressure sensor in line with the shift rod, as soon as you apply pressure to the lever the sensor signals the electronics box and kills the ignition for a predetermined amount of time, usually between 0.05 and 0.2 second.
This kind can be had for about 250 gbp.
The down side is that the injectors are still firing and with modern pistons having thin crowns you could conceivably shorten the life of your pistons through detonation because you have more than one measure of fuel in the cylinder when it starts firing again.
To prevent this there is another kind that also connects to the injectors but they are way more expensive and complicated to set up.
Edit
Just to put some numbers to this. At 8000 rpm the injectors and plugs are firing at 33 times every second.
So if you cut the ignition for 0.1 second you are still getting 3 times more fuel in the cylinder than you should have.