On my smartphone with a 4.7 inch screen running Android 4.1, I like MapsWithMe app (free) and the ability to download (on wifi) an entire state road map, state by state for offline use. If you know which states you will be in, you could load all of the state maps before you leave home. This is esentially a road map, not a cycling map however, bike trails not shown. I have used this app on a 7 inch android tablet but my tablet did not have a GPS chip so this was not as useful as I had hoped.

There are several other mapping apps that have good data for cycling, I use the cycling layer on Russian Military Maps ($11) and can load maps into memory (on wifi) for offline use later. This layer uses the open street cycling maps. But these maps are memory intensive and for that reason may be less than ideal for your use.

I am not suggesting these apps for continual use while riding, but they could come in handy when trying to figure out the next couple days of routing or looking for alternative routes if you have a detour. And if you get list, if you have already loaded the state map on MapsWithMe for the state you are in, it will show you where you are.

If you want to make phone calls when you have wifi, you can get a Google Voice account, set up the tablet with Google Voice and the app Groove Lite Ip Lite (free). But since this only works when you have wifi, it is not a reliable way to receive phone calls. It can also be less than convenient to use a tablet of this size held to the side of your head as a phone.