[wagonman76]

Sounds like you could do something like it with a regular speedometer with a partially covered long needle. Except make it so at zero the opening shows the base of the needle, transitioning to the highest speed where the opening shows the tip of the needle.

Another idea might be to take an Arduino and have it take the input pulses per mile, square it (and divide it as needed to scale it down), and send out the appropriate pulses per mile to the speedo. And have the speedo numbers adjusted accordingly.

The only tough part is that at low mphs, there will be very little accuracy to how fast you are really going, to make up for the huge scale of the larger mphs.