I like cellular tablets with gps for running radar omega app in the trucks while doing storm spotting. That way the spotter can stay abreast of wtf while the driver concentrates on not putting it in the ditch or too deep into the hail cores etc.
I use it all the time on the motorcycles. Its sort of free and does not require cell service.
Free version gives you ~5 state road maps and is a little basic. The paid version is like $40 and has global maps as well as things like topography and you can see things like gas stations and food on the map.
Yeah, I think it's worth it to have GPS on a tablet. I prefer it in the car so that I can keep the tablet dedicated to GPS and still have my phone free to use for whatever else. Also, on a long trip, keeping GPS going can cause burn-in on some phone screens. Even if the tablet doesn't have it's own Internet connection, just turn on the hotspot on your phone. I went with an Amazon FireHD tablet (with google play store added) because I wanted a cheap tablet. Since my phone already has a fairly large 6.9" screen, I couldn't justify an expensive tablet knowing that it wouldn't get used very often. But the FireHD tablets don't have GPS and that's the one thing that I really miss.