DIY Sensor Mattress ?

I have always been interested in a sensor mattress, and since a few years they do exist.
Could I make something like that myself ?

Small mats for babys are available a few years : http://www.angelcarebaby.com/item/international-monitor-with-sensor-mat-ac300/

But now also for normal beds and flexible : http://www.2mel.nl/research-and-development/smart-sensor-mattress-contactless-measurement-of-presence-respiration-heart-rate-in-bed/

This seems to use the same mat : http://lunasleep.com/

Force sensitive resistors ( Force Sensitive Resistor 0.5" - SEN-09375 - SparkFun Electronics ) can not be used, because they are not flexible enough. And about 400 * 5 would cost 2000 dollars, and the sensor mat is only 200 dollars.

This is with conductive yarn : http://specialtyfabricsreview.com/articles/0910_sh2_sensor_mat.html
At Adafruit.com they have conductive yarn and resistive yarn, but I don't know how that can be accurate enough for a rough weight indication.

They can get the heartbeat and breathing from the sensors. I think that is a lot of mathematical calculations, but it requires sensors that are sensitive enough.

My goal is a picture like this : http://www.tekscan.com/body-pressure-measurement

Is it possible to make that myself ? Or can I hack an existing sensor mat ?

You are doing a great project. Keep continuing. I wish your success.