iEngineer - handy pocket reference

...because you have your iPhone in your pocket, don't you?

And when you stand there wondering about what the recommended torque for a M12x1,5 grade 10.9 bolt is, whip out your iPhone and start iEngineer:

Start-up screen - iPhone 5s screenshot

And then select your bolt size:

Easy selection of screws - iPhone 5s screenshot

Hey, it even shows the pitch diameter! Nice! But swipe sideways on the top half, and soon you'll see

Ahh, there's the torque - iPhone 5s screenshot 

There! Now just oil the threads, set your wrench to 92 Nm and pull. What are those funny numbers instead of the signal strength bars? Field test mode!

Interesting that a bolt of this size and thread clamps five tons!

I find this app well worth having, packs a lot of useful info into your already crowded iPhone!
Couple this with MechTab if you need more thread data, like if you need to cut a thread in the lathe and don't have dies or taps. Those two apps can really make mechanical work easier.