Search for Gaia, Hema, Android Tablet, Bad Elf, Dual GPS and you will get lots of threads on this topic. Not trying to be a jerk but it helps to keep topics within existing threads. This way all of the good info is contained in one area. Requires less searching and lost information across a bunch of threads.
Me: iOS Gaia GPS Pro much more well rounded app than Hema but Hema is a copy of Gaia missing a few things.
They may one day equal each other but Hema hasn't been updated since release in May.
Delorme InReach for safety and GPS for iPad.
Ram Mounts Galore
Other Apps at my disposal: Avenza PDF Maps, Motion X, Pocket Earth, Maps.me, Waze probably a couple others I'm forgetting.
Because you said you were buying an android tablet you can look at Gaia GPS, Hema, Orux Maps, Backcountry Navigator to name a few. Again all of these solutions have been discussed in other threads.
2 small X-grip mounts for phone, Delorme, Ham Radio whatever I want. My rig has two mobile units but I have have some handhelds and those yellow Motorola FRS radios. So having options to lock stuff down when on dirt is helpful.
For my iPad