I've been reading Paul Graham, of YCombinator fame, recently; less to understand startup culture, but more because he has a good sense of people & culture and some of his thoughts echo mine.

<http://www.paulgraham.com/cities.html, http://www.paulgraham.com/love.html>.

On the other hand, he was writing about tablets and how he was impressed about their range of usages.

I wouldn't be surprised if by playing some clever tricks with the accelerometer you could even replace the bathroom scale.

Paul Graham (Dec. 2010) http://www.paulgraham.com/tablets.html

Knowing the large number of entrepreneurial types that follow pg religiously, I was surprised that a quick Google search didn't yield any results.

Not that I want to be the one to implement it, but I feel this this could be done with a rubber mat and your tablet. Place the tablet on the rubber mat and step on it. The movement, as measured by the accelerometer with dead reckoning, would be a good measure of the mat's compression, of which you know the physical properties.

Now, the problem is shipping a mat along with your app. An alternative is using an everyday compressible object (like a folded towel, bed, or shag carpet) that would just require some calibration and alignment to understand the property of the material. Place any known weight, say a 20lb bag of rice on it or a dumbbell, and you should be able to calibrate.

Since a usable number probably just needs to be accurate to the pound (as proven by the use of analog scales which require calibration and are hard to read), this method just may be accurate enough.

To flesh this out though, one would have to think more carefully about the market of bathroom scale owners though, as there seems to be a trend to digital scales with decimal accuracy. Alternatively, people might just buy it for the giggles, which on the app store is unfortunately a common reason.