Invitation Only (2009) is remarkable by two facts - it is first slasher horror made in Taiwan, and it features Japanese porn star Maria Ozawa in her first legit film. And I think no one would have noticed the first fact, unless the second one was there as well.
It seems that featuring porn stars in films is fashionable right now, it certainly can give a movie great publicity, and Ozawa is one of the biggest AV idols. Maybe because she did almost any available porn fetish, starting from schoolgirl, through bondage and to golden showers.
The movie was out in Taiwan in April, and you can expect its arrival to DVD stores in the near future. Oh yeah, in addition to Ozawa there is nice gore, killings and some kind of a story. Whatever.