Look into Motion X GPS HD. There is one for use in the car (Motion X GPS Drive HD) and another one for use everywhere else which is what I have. You can download maps of your choice to your device for use offline. Otherwise you can access everything when u do have a connection. You can also record, import, and export routes and waypoints.
I should also add that for Motion X GPS (the version I have) you can download topo and marine maps as well. The topo maps are useful for me for offloading purposes. You also have a choice for Bing, Google, or Motion-X road maps. Also I'm speaking as an iPhone user knowin that there is an iPad version so I don't know how it works with the iPad.