This being the mechanics forum, these guys are all pro's. Some of them have built hundreds of wheels.

As an amateur mechanic who will replace spokes and attempt minor truing I like the concept. If the tool will make it easier, and also substitute for some of the skills and knowledge of the pro's, I'd want one.

I like the idea of it displaying what the tension is. Going by feel and sound, the amateur can only be approximate and can't really tell how right his reference is. I'd also like the tool to grip the spoke while turning the nipple - I don't know if that's a feature that you're envisioning but it would be handy.

Something else that would really be useful, if the thing could automatically measure rim to hub distance and display a +/- number, to get a feel for how out of round it is. And also, feedback on how out of true the rim is at the spoke. Do that, and I'd want your tool.