Not unless the devices are all calibrated to use the same sensor.
And keep in mind you'll need to use a pullup resistor on the tach to get digidash to read it (if using a GMPP wiring harness)
The digidash is able to display all that on one screen fyi - speed, RPM, gear, water temp, oil temp, oil pressure
I'm a gauge guy myself - like seeing the needle move around - initially I thought about having a "normal" tach but after having used the digidash I'm very satisfied with it and glad I didn't do some aboration-combination of a digidash+ traditional gauges. I like the digidash so much i used it in my 917 as well...period correct you know, haha
-alex