I am getting ready to travel to Defcon and a lot of you folks are as well.
If you are in the market for a good VPN service give OmuraVPN a look. They provide 2 things for me.
1) they are encrypting everything from my mobile device and personal laptop. Sure, lots of apps use encryption but there are a bunch that haven't got the memo yet. This network level tunnel sends everything on device out a tunnel (except some unavoidable Cellular comm's done below the OS level)
2) they do adblocking off device. Without root. This is a battery saving method for me, since I really dont care about seeing ads - its more of an annoyance for me rather than a source of tin-foil hat hysteria that I see a lot of people subscribe too. But ad's do = less battery life so I like that.
If you are getting ready to go to hacker con's like me, and are looking for a quick countermeasure to the shenanigans that are about to happen with the wifi - check out omuravpn.com
Full disclosure, I know +Ryan R