The Pro Torque wrench should have a place in your toolbox if you care for your components and your safety.
With so much carbon and lightweight alloy kit on the scene, it has never been so important to tighten things to the correct torque. If the bolts on your components specify a torque value, they must be done up to that value. Not more, not less but that exact tightness. This means investing in a torque wrench and the Pro Torque Wrench from Shimano is a quality tool that you can wager your carbon frame on for its accuracy.
Covering a torque range of 3-15Nm the Pro Torque Wrench takes care of all the small delicate bolts used on stems, seatposts, 2-piece chainsets, etc - basically all the bolts except the big torque stuff like bottom brackets and cranks.
Dialling in the torque is easy: you simply pull the adjuster out and turn until the dial aligns with the desired torque reading. The tool has increments of 0.4Nm in a range of 3-15Nm with an accuracy of ±4%. This is more accurate than the torsion bar wrenches and the cheaper style of torque wrench with the graduated scale along the handle.
Best of all, the kit includes ¼ inch M3, M4, M5, M6 Hex, socket extensions and T25 & T30 sockets which should cover most of the bolts on a bike, although a T20 Torx could be handy for some.
It isn't cheap and you can pick up a torque wrench for half the money, but you can also pay a lot more. With the Pro torque wrench you're paying for quality and accuracy, so ask yourself: how much do you value your expensive componentry?