 Of course our research group offers custom build and advanced analysis of the data but first up you might not be ready for this and just want to have a play without investing too much. $300 bucks gets you an iPod touch and an excuse to get yourself one. If you are a bit more cashed up and dying for a reason to get an IPhone yep they have these sensors too. less than $100 will get you a Wii controller, or buy the full Wii system (tell you wife its for work purposes) you'll needa receiver to many laptops do this now. Or if you wan to get your hands a bit more dirty get the full range of inertial sensors and a blue tooth like from someone like Sparkfun iPhone iPod accelerometers
Wii accelerometer
6 DOF tracking from Sparkfun
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Sports Engineering >
Consider what you might want in a accelerometer sensor system? Memory, microprocessor, accelerometer, wireless connectivity and a nice user interface. We have been building these for a while now and then along comes Apple and puts it all in a box as a music player or mobile phone adn looks way cooler. See 
Its no secret that the new Wii platform by Nintendo has taken the world by storm with it revolutionary games controllers. Here they take acceleration sensors and use them to control game characters playing sport. Its just like measuring real people playing sport so you can anaylse them on a computer but the other way around and the hardware is remarkably similar. See 
Sparkfun are a neat company that sprung up in the US catering to the hobbyist that wanted to use specialist electronics but might not have the resources. Started as a couple of boys out of collegue they have rapidly gained a repuptation for quality low cost solutions. They have a range of modules including a range of inertial monitoring units. See