Below is a screen shot of the chart from within QlikView. attached is the extension object, the data and a QlikView application that utilises both. You now CAN click and drag the chart in a 360 degree motion to analyse the share of the data (initially that did not work). This aspect of the chart is very, very cool!
POINTS TO NOTE:
The chart does not work in IE at the moment. IE does not provide some of the inbuilt functionality needed to render the chart properly. It seems that 'Web Mode' in the QlikView desktop emulates IE so the chart wont work in the desktop client either. You will need to deploy the extension to the server and view the QVW from there with a non-IE browser. I used Chrome but others should work.
I have not changed the extension object code to a QAR, as it wont work within the desktop product anyway (see above). Simply unzip the code to your server directory C:\ProgramData\QlikTech\QlikViewServer\Extensions\Objects and copy the QVW to your server.
Note that the chart API itself does not auto-scale. It displays the results within a 0-1 range. For the moment you can get around that by 're-shaping' your data to fit that range.
If there are zeroes in your data then QlikView doesnt pass them to the chart. To get around this you need to add an extra expression to the chart that always equates to a number eg. sum(1). The extra expression is not used in the chart, but forces every row to be included.