I don't know how the Prius layout is, but yes, the Accorn Navi does provide instant readout and data - however, it's in a bar graph, so it's not exact; but it is very helpful in knowing how you're doing and what will improve it.

As most (I guess), it has a setting to automatically reset with each fillup and has a history button showing the previous one tank, including miles travelled, mpg, average speed, and time driven.

In addition, it has two trip meters with each having an independent mpg reading that resets with the trip.

Hope this helps and I didn't leave out much....

'05 Accord Hybrid
'05 Odyssey EX-L
'03 1800 Goldwing
'98 Civic EX (16 yr. old daughter's)