Evening, Mark. No, it can't be added. The NAVI unit/screen is an integral part of the system controlling the audio, a/c, and trip computer, along with other options.

With that said, it IS worth it. I've NEVER heard someone say they wished they'd saved the money and bought one without; BUT, you can find NUMEROUS posts on this site stating their regret for not getting one.

You can buy dash mounted units, but the Honda OEM unit is incredible, PLUS the trip computer is invaluable in FE feedback.

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