DIY'ers and carpenters know the trick of using a piece of string to measure something you can't get a tape measure around; you wrap the string around, say, a pole, mark it, measure the string, and now you've got your circumference (and can calculate the diameter).
The Smart String Tape Measure finally encapsulates this practice into a tool. The retractable string corresponds with an on-screen display that gives you the dimension, which you can then plug into the equation of your choosing; it even stores multiple dimensions, which will come in handy if you're measuring-&-CADding. The industrial design of the tool itself looks pretty lame, and I don't like that it's one more thing you have to carry in your toolbox and that it's delicate, but if you have to measure a lot of irregular surfaces it's probably a damn sight quicker than marking and measuring string.
The tool's popularity has outstripped production; at press time the $11.99 item was out of stock, but the next shipment's due in just a few days.