There are not very many 'well done' applications for engineers in the Windows Phone Marketplace. One of the best is "MDCE - Mechanical Design Project Cost Estimation" even the user interface is a quite clumsy. But I found out the developers web site
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that there will be an update to version 2.0 very soon. As I loaded the version 2.0 manual, the enhancements seems to be really fine. Anxiously waiting for the update, somebody has done a truly great job!