I've considered this, but haven't pulled the trigger yet. The Skyroam is on T-Mobile I think, but like I said - so far that device hasn't impressed me.
I think the LTE iPad that another commenter suggested is the best option I've seen so far - that would be great to take calls on, and should leave enough hotspot data for other work on my laptop.
I am out of range much less on verizon.
I wonder if it's worth it for the OP to have accounts with more than one company.