$.02 on the product. I would never buy it because your form factor is unstable and unlikely to work.
I have used the Garmin Nuvi Dash Kit, and it isn't great. but it is still light years ahead of your design. It does 3 things yours doesn't, soft on bottom to keep from scratching, wide distribution with rubberized bottom to not slip, and it easily detaches the device. Conceptually you are on to something, implementation wise it looks like it will fall over every time I round a corner.
Search google images: garmin nuvi dash kit
Good luck with the next iteration!