As seen in Popular Mechanics Magazine! 
The Powerbuilt 3/8 inch drive Digital Torque Adapter converts any standard 3/8 inch drive ratchet into an accurate digital torque wrench.  Simply set the desired torque value, plug in a ratchet and socket and tighten the fastener until the digital display and audible tone indicate you've reached your target torque.   You can also use it to calibrate an existing torque wrench right in your own shop or garage.   Display modes include Peak, which displays and stores the max torque applied, and Trace, which shows real-time torque as it is applied.   Selectable for five torque units of measure: lb-ft, lb-in, kg-cm, kg-m and N-m 

Features:
Torque Range: 20-99 lb-ft
Accuracy: + /- 1%
Battery, Storage Case and Calibration Cube included  

Watch a video here:

http://www.youtube.com/watch?v=_EeQeH5YAcA