gps is the cheapest replacement speedometer there is
I've had two vehicles in the past where the speedometer decided to stop working. Each time it was well over $100 to fix - and bear in mind this was over 5 years ago. On one of the vehicles I had to custom order a gauge cluster, and for the other the cluster was in stock in the shop.
If I had a speedometer bust today I wouldn't even bother replacing it. Instead I would purposely buy a Garmin nüvi, use double-sided Velcro and stick it right over the busted speedometer.
This is what a screen shot of it looks like:
Whether you use the 4.3-inch widescreen the 3.5-inch standard screen, the information is the same. Since it has anti-glare coating on it, sun glare isn't a problem. Signal acquisition isn't a problem either.
How accurate is it? I guarantee it's more accurate than the speedometer you have in your car now.
The only real drawback is the power cable. You have to find some way to snake it through in or around the steering column to get to the cigarette lighter port. But other than that, that's the only drawback.
I have - and I kid you not - considered doing this on a gauge cluster even with a working speedometer, because the best position for a GPS is right where the gauges are. My reasons for not doing it are because of the cable and that it blocks the fuel gauge. However if I had a 3.5-inch instead of the 4.3 I could totally do it.
For the next car I get, one of the first things I'm going to inspect is the gauge panel just to see if I can do this. 🙂