Fairlay is a word which will help me but still I couldn't find betting on some price (of Bitcoin or something) every few minutes.

Trading with leverage is completely other thing. Maybe I will explain a bit my strategy.

On btc-e if 1000 dollars were bet down and 10 dollars bet up, then if I bet down 1 dollar I could win (10/1001)*0,95=0,094 and if I bet up 1000/11*0,95=86,36 (every time you win on btc-e you have to pay 5% fee). In any case the broker win some money, so I'm not broker's opponent. My opponents are other people, so it is much easier to win (long term winning is possible here). It is easy to see that if I somehow calculate that the probability of win if I bet up is greater than 1/86,36=1,16% then I should do it. Similarly you can calculate it for betting down. To calculate this probability I'm using ARMA-GARCH models (that's why it is different than in playing with leverege).

So I'm still looking for some betting site against others, not against broker.