Tach for Prius C ?

You may have bought the wrong car. Tachometer Window Decal is about the only thing I can suggest.

 

ScanGaugeII shows 4 OBD values at a time, including RPM. I'm using it, pretty much always showing RPM, Coolant Temperature, Instant MPG and Accumulating MPG since last start up.

 

And yes I use RPMs as one of my Scangauge II gauges, if nothing else it is interesting to see that RPMs relates to MPG

 

I went with the lower priced but larger display UltraGauge.
All I simply wanted was Tach, outside temperature, coolant temperature and charging voltage displayed.
UltraGauge does it while looking good on the eyes and in the car.

 

^ I find Coolant Temp very handy. The Prius have a suprising absence of gauges. Maybe a blessing? If you care you get add-on gauges that are more accurate/imformative than the rudimentary built-ins.

 

I run the torque app on my android phone running through a $15 bluetooth obd2 adapter. Works great.