Dear all
I have received some informative private replies about accelerometer and step counter, here are some of more helpful reponses.

Thanks to all who replied.

Farzaneh Yazdani
Research Officer
SUMS,School of Rehabilitation, Iran
Tel: +98-711-6261081
Fax: +98-711-6272495

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IF you are looking for a wireless 3D accelerometer, then check out..zeropnt.com They have been very helpful in customizing to our needs. I can not recommend a step counter. We have been using the wireless accelerometer to look at jump impact in sport.
Good luck w your research,

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Hi Farzaneh,
The Step Activity Monitor (SAM), a microprocessor-driven
accelerometer that measures walking activity might suit your requirements.
We have used it in the past for persons with spinal cord injury. You might
want to look into it.

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Hi Dr. Yazdani,
Please don't summerize my comments to BIOMCH-L.
Getting all those variables is hard to do. I have used StepWatch Activity Monitors (Orthocare Innovations, Montlake Terrace, Washington, USA) to collect step rate data, but stride length is difficult. A measurement of step length might take something like a gaitrite mat. StepWatch Activity Monitors are about $550 USD each and you would need a docking port (about $1000) buying 11 with a docking port is about $7000 USD.Actigraph or actical both measure "activity" with accelerometers, and are in the $500 USD range, but I have no experience with them.
There is a really cool sensor made by Catapult (http://www.microtechnologycrc.com/index.html) which collects a huge array of data, but is very expensive, maybe $3500 USD each. But this still does not have step length, but with 5Hx GPS it gives you speed and position and turning in 3D with a magnometer. It also has an accelerometer to detect collisions, falls, etc. Best of luck.

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Dear Farzaneh Yazdani

For accelerometers. Please check the website

http://www.zeropnt.com/

We have also used the accelerometer as step-counter and cadance meter.

email
alex@zeropnt.com
for more details.

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I've used the SAM (step activity monitor) in the past.
http://www.orthocareinnovations.com/category.php?cat=1013

I have also heard good things about the Actigraph
http://www.theactigraph.com/