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March 15, 2010 4:10 PM

Is it possible to manually extract and analyze the data from a personal accelerometer?

Recently, I've started hearing a lot about personal accelerometers such as the FitBit and Philips' DirectLife. Before I buy one of these, I'd love to know if there's a way for me to extract and analyze the data in these accelerometers without always using their associated web-sites (especially the $12/month web-site that Philips uses). Does anybody know whether this is possible and, if so, whether there is anything published about the process?

posted by eisenkr to Computers & Internet (4 answers total)

I've tinkered with 3 dimensional accelerometers before. They're relatively simple, but low level. You supply a power voltage and it outputs the forces as a voltage range.

If you're asking how to hack these specific tools, worst case scenario is you open it up and add snoop wires to the X, Y and Z outputs. It's not like there's an ANSI standard for this kind of data, and even if there were, nothing would force anyone to use it.

I have to say, it's pretty creepy for the DirectLife FAQ to include the question:

Q. How difficult is it for HR to implement DirectLife?
A. It is not difficult at all. A Philips Account Manager will meet with your HR department to determine your needs. He or she will then develop a tailored rollout plan.

Judging by the followup question, I'm going to assume there's data encryption on board:

Q. Can my employer see my activity data?
A. No. Your employer cannot see individual data. They can only see aggregated data, which is data on group level and has no reference to any individual.

posted by pwnguin at 4:39 PM on March 15, 2010

Certainly these devices are hackable but given that they're a little expensive I guess no one has done so yet. But it's just pulling the data via USB and certainly that could be reverse-engineered. I doubt there's much security on the device itself.
posted by GuyZero at 4:44 PM on March 15, 2010

It's probably a lot easier to use a device which has tools to analyze the accelerometer data, rather than deal with the raw data generated that is probably handled in a form designed for the embedded processor.

By comparison, an iPod touch is cheaper. There's also the Texas Instruments eZ430-Chronos, which is a programmable "watch development tool" with an accelerometer. These have APIs and development tools.
posted by meowzilla at 5:10 PM on March 15, 2010

This doesn't exactly answer your question, but I figured I would throw in a data point..

I have a FitBit (it rocks). Supposedly, they are building a JSON/XML API to access your data but one doesn't exist yet. I've tinkered with the site a bit, and it's pretty trivial to pull your data out of the XML feeds that feed the flash graphs on your FitBit 'dashboard'. The FitBit USB receiver is pretty black-boxish. With Little Snitch, I've noticed that it sends off a POST payload to the FitBit website when the device syncs- if you had the motivation, you could probably intercept the data and grab all of the raw data points from your FitBit w/out having to go through the website.
posted by adirondack at 5:20 PM on March 15, 2010