Replaced tires on 2009 CLK350 and was dismayed by how the prior shop [over]torqued the nuts (discovered trying to put mini-spare on after AAA trailered it home late at night) (http://www.benzworld.org/forums/w209-clk-class/2085346-ok-use-anti-seize-lug-nuts.html
). Being more the cycling mechanic than working on cars (like in the old days), I found my 1/2" clicker torque wrench croaked from corrosion or something. So I knew I wouldn't be able to check shop torque values without buying a new torque wrench.
I found a review of a Pittsburg Pro torque adapter that actually tested it (and some others) with lab equipment and found it awesomely accurate. I bought one through Harbor Freight for cheap (~$40 including tax and shipping).
Totally excellent and highly recommended.
A link to a video of how it works is here:
Contrary to the reviews, it works just like you'd think. Turn it on, use it, turn it off. It stores torque values in memory, but by the time I ever remembered how to retrieve, it's easily reset with the +/- keys. Also neat was that when you press a +/- key to set the torque, it starts at 100 Nm, so you're never far from the desired value.
A photo of what comes in the box (and how i cut a little hole in the foam and shaved the egg crates a bit to take pressure off unit... and even how I folded the instructions and calibration paper). I included this because some of the reviews are silly in their complaining about trivial things fixed in a minute. (And yes, I have a killer 17 mm, 6-point impact socket for this... I love buying good tools...)
Summary: Very satisfying to use. Easily put in a vise to compare to a beam wrench or clicker. Beats any clicker hands down.