I would like to see a native player for mobile devices that will allow clients to demo the app workflow. While the PDF export option is available it is relatively basic. I would also like to have a mobile player quickly available so I can test without the need to transfer to a mobile device. Please take a look at proto.io to see what I mean. They have some interesting ideas but I find using Balsamiq much more intuitive and quicker to use. I know these are only Mock ups but I think clients / users are becoming more demanding and want to see better looking designs.