We got one of these for campgrounds with weak signals and it works well.
http://www.ampedwireless.com/family/repeaters.html You do need a laptop to connect this to just to start at the campground. Plug this into the laptop with a network cable and software will start which guides you through locking the signal source into the repeater. Once you have it set, you don't need the laptop connected again until you get to another campground and a new wifi signal. It can't be set up with a tablet as it needs a network cable to connect with for setup.
We have gone from a weak signal to a very strong signal at campgrounds with this.
