The first customer review says it doesn't work...
Yes, I saw that after I posted. I sent an inquiry to the company about the DR. I asked what cities it covers and if you need to be online to use it.
They sent back that once you download the App it works without being online, and it says all cities in all countries they sell are covered. But I don't believe that part, as usually GPS only works good in SD and Santiago. I will pass on this one.
google maps is all I need
Yep Google maps works pretty much everywhere and I just realized my GPS on my phone works (Here in Mexico at least) without having data turned on. That's GPS and maps alone, not turn by turn navigation with voice for that you need to download data, but still you can see where you are down to a few feet and what roads you're following. I haven't tried it in The DR, but I would think it works the same as well.