I'm Marko and I sell a gadget that projects speed onto your windscreen. (SpeedView daylight visible Head up Display)
A couple of photos and a video:
The speed shown (kph or mph) will be correct no matter what you've done with tyres/gearboxes/differentials, and shows up well on trackday cameras too. This sits in your peripheral vision to reduce the time spent with your eyes off the road and unlike GPS based devices, there's no lag in the display. Looks flair too - perhaps you want it just for that.
Everything is easier to fit with photos and a few tips and tricks from somebody who has fitted one before. Real enthusiasts and customers write the best "How To" guides, so if you write a quick guide to share with others I'll discount your SpeedView to just £40 (including delivery) to say thanks. (retail price £69.99)
My website has more details and FAQs:
https://www.speedview.co/
Here are the universal install guides and tech specs:
https://www.speedview.co/faq/download
Think you might be interested?
Questions? Feedback? Ask here on the or on info@speedview.co