My $49 Kindle Fire is one of my favorite devices. It's cheap enough that I don't worry about something happening to it and it's light enough to be comfortable to hold.
I've always lamented the inability to use Google Hangouts on it, though. (I know I can install Google Play Services on it but that introduces quirks and error messages into my daily life that I'd rather not live with.)
In the RingPlus days I used CsipSimple as a way to make and receive calls via Fluidcall. And, since I frequently receive calls on my Google Voice number, I would forward them to one of my RingPlus numbers-- which rang them through to my Kindle Fire.
Now that those days are gone, I use the Magic Jack app on my Kindle Fire, instead. (We have a Magic Jack as our home landline.) With the Magic Jack app installed I can make and receive calls (despite the message that says that Google Play Services are required in order for the app to work) and I can forward my Google Voice number to it, as well.
With the Magic Jack and CellNUVO apps installed on my Kindle Fire I've got all the functionality I need when I've got idle time in front of the TV.