Defi-link HUD display & gauges
 

I have no experience with these products, but they certain look like fun. Here's a description of one of the products:

PRODUCT FEATURES
Defi-Link Display VSD CONCEPT is a product to display information on the speed, engine speed, and so on by reflecting the information on the windshield of vehicle. The projection technology is called "Heads Up Display(HUD)." VSD is our original technology focusing on compactness and universality utilizing the HUD technology. <<Detailed commentary on VSD>>

By connecting this product to the Defi-Link System, oil temperature, water temperature, oil pressure, fuel pressure, and exhaust temperature can be displayed other than speed and engine speed.


Defi-Link HUD