If you are interested in setting one up for yourself, It's pretty easy with the instructions provided by the @eff but you can also find help at the GitHub page.
I bought several of the cell hotspot units for only $11 off eBay.
I did mine in about 10 minutes (5 of which was looking for an answer on the GitHub page for something happening on my Mac when I went to flash the device) and it appears to be working fine.
Be sure and read the section on reporting results back to #EFF too!