If you want to have in your car a heads up display, this product might be exactly what are you looking for.
Wired or Wireless:Wired
Size: 3.5 * 2.1 * 0.5 inches ( 90 * 54 * 14 mm )
Functions: Speed, Rpm, Water temperature, voltage
Certifications:CE, ROHS, FCC
Display Size: 3.5"