While I can't vouch for how well it actually works, the concept behind Karma is undeniably cool. You buy their mobile 4G hotspot device, when you use it an open Wi-Fi network is created and whenever someone connects to that network, you're rewarded with extra bandwidth. So, instead of hoarding the data share for yourself, your account gains from the social interaction. Conceptually solid and the actual device, software and website are all gorgeous looking. I don't travel quite enough to actually use it but I can think of some folk who do.