An interesting review.
http://fstoppers.com/fstoppers-revie...-tethered-ever
The 6D has wifi (and an app) for this sort of thing, but that doesn't help in the field if you can't connect both devices to the same wifi. I guess you could run your phone as a hotspot?
Anyway looks interesting.
Pretty pricey at $300, though the reviewer thinks that's a steal.