hmmm.
Somewhere it is written that "plug-n-play into Arduino" is defined by male headers? Here is a photo of the sensor plugged into the UNO. Yes we are using male/male jumper cables (in the photo), but hook-up wire can be used too.
We are calling it "plug-n-play" b/c when you plug in the sensor and upload the Arduino code (we provide), pin 13's LED blinks realtime to your heart-rate. The code turns data from the sensor into something useful, like a "beats-per-minute value". We've also included Processing software that graphs your pulse and bpm in realtime. It does all of this before you modify any code.
This is a tool for developers and makers. There is still like 10 mins of prep work (with a hot-glue gun) to the sensor before you can start using it. Given that I've seen students and colleagues unsuccessfully spend months to get the functionality our sensor provides in 10 minutes of prep, I think "plug-n-play" is a fair term to use.
There is so much more to this project then the female connector we used. If you are interested in more of the meat of the project, take 2 mins to watch our video. It shows the sensor being plugged into Arduino. Yury Gitman - YouTube
We'll be publishing a "getting started guide" shortly, that will have more details then our current site. But there are a few more photos here for now: http://pulsesensor.com/