I would like an ELO rating system like this: http://online-ladder.de/index.php/en/leagueUser/index/id/4 or as it has the ESL.
Here it should be possible to challenge opponents by pretending the day and time. The opponent must confirm this and then the SPIEL is entered. Both parties must confirm the result, and this should be noted in the table. How the ELO system is calculated I can not say unfortunately directly.