You might be interested in http://www.augur.net/. Although, I believe it uses its own native token, rather than being built directly on top of bitcoin or ethereum.
Hey thanks for sharing our project on this post! Just wanted to clear something up from what you said.
Augur's native token is not what is used to create markets, Augur's token is Called REP (short for Reputation) and holders of the token actually serve as reporters that serve as the basis of our decentralized oracle system.
We created a few resources to explain how REP works including how REP holders are rewarded for reporting the truth/punished for reporting lies. We created a short two minute animated video to explain this process you can check out here: https://www.youtube.com/watch?v=sCms-snzHk4.
Additionally there is a great resource going into much further detail about Reputation as well as an infographic to visually illustrate the process here: http://www.augur.net/blog/what-is-reputation
Augur is built directly on Ethereum. Truthcoin will be making its own chain. I don't care who wins, and to be honest I don't give either a very high chance. I really really think prediction markets should exist though, So I applaud both efforts.
One real big problem is nobody wants to bet using shady highly volatile currency like Bitcoin or Ether. I'd much prefer USD markets, Vitalik has some ideas about making stable coins that track USD. Hopefully that works out.
the DAI project (originally eDollar, which is now intended to be built using DAI) which tracks a value which I think is like, some basket of different currencies, is being worked on.
I don't really understand the mechanism by which it is meant to track the price of the basket of currencies, but I haven't seen many criticisms of it?
Augur's native token is not what is used to create markets, Augur's token is Called REP (short for Reputation) and holders of the token actually serve as reporters that serve as the basis of our decentralized oracle system.
We created a few resources to explain how REP works including how REP holders are rewarded for reporting the truth/punished for reporting lies. We created a short two minute animated video to explain this process you can check out here: https://www.youtube.com/watch?v=sCms-snzHk4.
Additionally there is a great resource going into much further detail about Reputation as well as an infographic to visually illustrate the process here: http://www.augur.net/blog/what-is-reputation
Finally feel free to reach out if you have any other questions. The Augur Alpha is out at http://demo.augur.net and our code is on github at http://github.com/augurproject