I get a magazine at work called "Design News"--in the back there is a section called Gadget Freak Files, which appears to be an ad for Allied Electronics. Anyway, there was an interesting project to build a dry air density sensor/calculator for a Palm. The link to the online article is
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If the link wraps go to
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and look down the left for "Gadget Freak". On the GF page, look for case #40. There are some other cool projects there, too!