Hey - Haven/OpenBazaar developer here. We've been working hard on this for a long time. There are a lot of little snags when it comes to running a p2p ecommerce system where you own all your own data, and then making it work on mobile, but we feel we've done a pretty good job at tackling them in a say that isn't a UX disaster. If this kind of thing is up your alley I hope you try it a and find it pleasure to use.