Even with its belt full of powerful tools onboard, Smart Tools is, for the most part, simple. The app opens up to a wall of choices, and if you've used any of Smart Tools' apps before, then all of them should look familiar. Smart Tools combines the powers of all of the developer's individual Pro tool sets.
The first set lets you measure length and angle, using a level, ruler, and two protractors (one which uses the screen, and the other your device's camera).
The second offers a Distance tool, which is a bit more complicated, as it requires you to do some calculations of your own.
The third set uses your phone's built-in compass to either indicate direction or measure magnetic field for use as a metal detector. In my experience, these worked well, but performance may differ, depending on your specific device.
The fourth set is a flashlight, which can fire up either your LED flash or your screen, for use as a light source.
Finally, there's a Sound and Vibration set, which, you guessed it, measures the levels of sound and vibration that your device is subjected to.
Overall, I think this full set of tools is incredibly useful, and a steal at only $2.50 at the time of this review. In fact, the way I see it, Smart Tools' functions should come built into every Android device.