While there are a crap ton of different pressure sensors out there, which ones are appropriate for integration into the slip suit? There are a number of requirements that have to be taken into account:

• The sensors have to cover a large surface area.
• The sensors have to be able to locate on the sensor where a force occurred.
• The sensor has to respond fast enough to register an injurious impulse.

While these are pretty vague; they do not take into account sensor processing or possible power requirements or other details necessary for implementation, it's a good basis to begin selection (or at least rejection) of sensors. 

A set of sensors that we cannot use are any that rigid surfaces for pressures to be 'sensed'  (i.e. rely on the response of the material to hard backing). This is would be a problem with the sensor suit as humans are notoriously squishy and anything that requires rigidity would not work. Since this suit is for sports we cannot impose some sort of rigid backing as that may decrease the mobility of the user. 

Another issue is that some of the sensors are may not be durable enough or fast enough.  Felt sensors strike me as particularly delicate and probably are not the best idea for sensing hard blows. I am also unsure of their response time since quick impulses that cause injuries may be too quick for the sensors to pick up. 

Other sensors such as PZTs are extraordinarily rigid and pretty tiny. Since our idea requires sensors that cover a large area, these probably arn't the best solution.

Two sensor types I'm leaning towards are resistive and capacitive sensing though use of polymer foams and conductive polymer sheets.  For capacitive sensors we are going to take a dielectric foam and attach two conductive electrodes to the ends. The squish of the capacitor will provide us with a force measurement. Additionally Zoflex conductive sheets will provide some resistive pressure sensing. Localizing these sensors can be done with some intelligent design of the electrodes and  making multiple arrays.

Here is a video I made of one of these capacitive sensors working with a simple ATMega circuit a few years back:

https://www.youtube.com/watch?v=qJrnLTnaMTs

Additionally we'll probably implement some techniques discribed in  "Soft Wearable Motion Sensing Suit for Lower Limb Biomechanics Measurements" [ICRA 2013]