I think I've invented a touch screen Promethean

I often wondered how Promethean pens required no power whatsoever to work. Most other solutions require you to stick an AA battery in them and you’ll get a year or so out of them before having to replace the batteries. Promethean pens will go on for ever and ever relatively. So I asked the head of development and he told me that there is a coil of copper wiring through the pen which reacts to the wiring inside the whiteboard. This got me thinking about a touch screen Promethean board.

One of the weaknesses Promethean boards have is the inability to use your finger to interact with it. Promethean have given me excuses of why they “chose” not to. Hygiene, quality and sturdiness of touch-screen surfaces, children should be using pens not fingers to write, etc. etc. None of them wash with me.
Hygiene is scare-mongering – I’m sure the same germs go on the pen as the board. A touch-screen surface doesn’t have to be less sturdy (as you’ll see). Children should probably not be writing with their fingers but they certainly should be dragging and dropping using them – that’s more natural. The pen, of course, should also be available.
So onto my idea. I really think this is an idea that could be used so if it is released in the future, I’m taking the credit!
My idea is to make a device that would either take the form of a thimble or a ring (jewelery). I prefer the ring because it would be easier to make it adjustable to different finger sizes. The device would contain the same copper coiling as the pen and when you slip it on your finger, voila, you would then be able to interact with the board using your finger! Moreover, it’s easy to stick a “right-click” button on one of these thus making them better than an ordinary finger.
And if Promethean are reading this, I’m even willing to be the guinea pig.