This allows you to read the Air/Fuel mixture, which is useful for tuning your carb. If like me, you are not confident enough to work it out by ear, spark plug tests etc. Well, it is accurate so I think the tuning process will be faster and more accurate. You can get a readout on a data display on your dash so while riding at the points where the jets come in on your carb you can see exactly the effect and accurately re-jet – also for adjusting the idle. It can also show you the effect of seasonal and altitude changes, so you can make informed decisions on when and how important it may be to adjust the carb for those changes.
These are being sold on e-bay for US200 at the moment, but it looks as though they are being superseded by the LC-2 (http://www.innovatemotorsports.com/products/lc2.php). You just make sure there is a kit with a gauge or you add on a gauge to your order. I also ordered an extra bung and screw plug so I could swap my sensor between the front and rear exhausts to measure both cylinders.
Here is a picture of the pack I used.

To install:
1. You will have to take off your exhaust pipes and get the bung/s welded in. I took mine to a motorbike engineer. I think it cost me $50. I got an extra bung (ordered 1 extra) put in so I could swap the sensor over to measure both cylinders. As per Innovate's suggestion I cut a piece from a copper pipe, drilled a hole and used that to displace heat when you screw in the sensor.

2. At the other end there is the readout gauge. This could either be mounted on the dash where the clock goes or on that dash strip.

3. Wiring
Follow the Innovate instructions to wire up the the gauge with the Wideband controller, the gauge and the bracket. I then enclosed the bundle of wires in some heat shrink (not shrinking it) and bound it up in electric tape. The Innovate supplied bracket that the wire bundle is attached to can now be bolted on to the horn attachment.

This also requires a fuse for the power/red wire and, to attach it to the horn, wiring into the horn green wire.

4. Connect up the Wideband sensor and controller. The wire from the sensor can be fed up to a point on the frame and likewise the Wideband controller can be fed from the horn attachment to the same point on the frame and the two connect up.

4. Calibrate the sensor. In the picture above the small circle is around the small red flasher and the larger red circle is around the red push button. These are used to calibrate the sensor - which is done with the sensor out of the exhaust pipe. After doing that screw the sensor back into the exhaust.
6. Done :-) Now when you start the bike it takes a few seconds and you then get a readout on the gauge. Here the gauge is showing 13.2 at idle. 12.8 – 13.2 seems optimal across the jetting range with early 12s to late 13s being fine. The figure is the amount of air to one part of fuel – known as AFR:

NOTE: There are also two wires from the Wideband controller that can plug into your PC and with the innovate software you can record a graph readout. I tried this with a laptop in my backpack, but really I don't think it is needed. Riding and checking the gauge readout in real time seems ample enough feedback for your carb jetting decisions.