If you're talking about for your camper, it almost certainly won't work. The subscription is geo-locked to an IP address and zip code and you can only change it once. It is not intended to be used from multiple locations. And as lryrob9301 pointed out, you'll need a good internet connection with no data caps.
If you're talking about for your home, it works fine. You have to initially set up your account from either an Amazon Fire TV (or Stick) or Roku. After that, you can install apps on any of your devices and view on them. There is no hardware, it's all software. It does have DVR capabilities, but they're a little different than you may be used to (it doesn't keep track of what's been watched and what hasn't, you can't delete recordings, it keeps all versions of a show for 28 days so you can't pick and choose between new or repeats).
If you are talking about Sling then the info is wrong. I have been using Sling for the last year after I cut the cord along with my OTA tivo. The tv in my camper is a Roku tv and I can turn on my phones hotspot and watch either what has been recorded already or live tv from Sling.
You dont need to sign up on Amz stick or Roku if you dont want to - you can do it from your computer. You can also watch tv from your computer as well if you want to.
The DVR feature does let you delete shows, and it does keep track of them so you can set it up like a regular dvr to only record new shows etc...
The subscription is not locked into anything. I can watch Sling from any computer, my phone, my tablet etc...anywhere I have cell signal or wifi.
The same is true with my Tivo - although I also needed to buy a Tivo stream unit - to be able to stream it or download the recorded shows to my device.
I tried PSVUE but they didnt carry one of the channels i like history or discovery or something and Sling did, plus with their promo you got a free roku streaming stick.
At home I have the app installed on a firetv box (wired) and upstairs bedroom is the Roku (wireless) I have no problems with either of them