-- Last Updated: Nov-02-12 11:15 PM EST --
Garmin sells the Montana as dual purpose GPS. If you add the Navigator maps it should work just like a Nuvi. It has a bigger screen then most handhelds which does help in the car, does have spoken directions and lane assist. They do not offer lifetime maps which is a major flaw in my mind.
It is bit expensive for me, esp if you keep updating maps.
I have the Oregon but I still use an old Nuvi in the car as I bought lifetime maps for it awhile ago, it has traffic updates and the screen is a bit larger.
On the Oregon I loaded in free road map which works very well, as long as you don't care about lane assist, traffic updates or voice directions which I mostly turn off anyway. Overall, it could be used as mixed used GPS with slight limitations.
The Nuvi's are pretty cheap now -- there has been a number of recent Groupon deals on a refurbed Nuvi well under a $100 with lifetime maps and traffic I believe. The maps are what really cost you in the end and where I am we have a number of big road projects, as well as new housing developments that are constantly changing the maps.
I have also used Android phone maps but overall they let me down to often when actually lost in the boonies with no service. The user interface is horrible when you need a to find a restaurant or gas station when you don't have a navigator next to you. I now use my Nuvi instead of smart phone.