BTS, NXT, XCP, PeerGroup, and XEM can create 'pegged' assets to do this....
A wide array of ALTs can collectively serve to do this ... all in the open public market arena.
Nxt has 'em: superBTC, for one. Asset ID 12659653638116877017 .
The trouble, as with all pegged assets, lies in the spread. Not enough market-makers/liquidity --> too big a spread. Too much slippage, if you will.
As for which comes first, the liquidity or the market-making, I found out that you need the liquidity before the market-making. Suffice it to say, I found this one out the hard way.