For all mahjong players who want to play on their smartphones,
Mahjong By Green Tomato Limited
Jo VandeWeghe (Belgium) collected a series of games for these various devices. The various rules (HK, Riichi, MCR, Taiwan) are available according to the downloaded games. (Interview of MahjongNews)
Most of these games are available directly on the dedicated platforms such as iTunes (for the devices of iPhone, iPad, iPod)
But to spare time, Mr VandeWeghe put all the links on the same site : http://www.dipching.com/iOSmj.html
For each of these games, Mr VandeWeghe summarized some general information (cf example below).
Some games also listed for the devices of type "Palm", "PSION" or the others else.http://www.dipching.com/palmjongg.html
Below some screen shots of applications