Really straightforward download tethergps on nook color n your phone. Connect both phone and NC to the same hotspots.
to enable navigation you can do 1 of 2 ways:
1) Nook color + Android Phone w/ GPS + same network +tetherGPS app
2) Nook color + Bluetooth GPS + Bluetooth GPS app
Turn on tethergps client on nook, tethergps server on the phone
Launch Google map, type destination, select navigate
Make sure nook has 'allow mock locations' checked in settings/development and make sure GPS is checked as well
now the other way to enable navigation is to but a bluetooth gps - you can get them as allow as $25 from amazon - i got mine for $35 - these gps units export a standard datastream that nook can read but in order to do so, you must install an app called bluetooth gps in the nook which recieves the data and makes it usable by location based apps. This is what i use primarily
now the caveat with either of the above is google maps need a wifi connection to download the maps. you can opt for a $5 app called copilot which lets you navigate without a wifi connection. Now the issue i have with this and the app designers tell me they are worknig on it - is that when you enter an address as a destination, it looks for an activation code which means you need to be connected to wifi, but after that you can disconnect and it will work. I use this as well
i am now downloading a free map called MapDroyd which is also a navigation app but it lets you download maps locally so you don't need to be connected to wifi