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Well you have Athos clothing trackers coming out soon, which tracks muscle exertion.

Thing is although, it costs $300-$400 dollars. Runkeeper works with the phone you already have, and you can optionally add a couple of $50-$150 accessories. Very different price points.

This might have promise to what you're thinking of:

http://www.liveathos.com/

Skip the complex sensors - I'd be happy just to have a low friction interface for recording lifts.