I have no idea whether Selecta7 works or not, but I can tell you that all arguments about not being able to put a bet on if you are a winner are completely finished.
Any of the betting exchanges can be used to get as good or better prices than the bookies, and they don't care if you win because you are beating other punters. Many bookies are on the sites laying odds on all the runners in every race, and you can do the same yourself if you have the skill. (Few do, I imagine).
As betting guru Geoff Harvey proves, there's never been a better time to work on systems for all sports betting. And it will get better as more mug punters migrate to the exchanges.
With some services you can trade a football match in the same way you trade futures. Like trading futures, I assume it takes time and experience. But if it ever really takes off and hits the mass market, free money beckons.