Smart tools is an excellent "All-in-One" App which provides Five cool sets of tools. It is one of the trending educational apps in play store right now.
Set 1: Length, Angle, Slope, Level, Thread - Smart Ruler Pro
Set 2: Distance, Height, Width, Area - Smart Measure Pro
Set 3: Compass, Metal detector, GPS - Smart Compass Pro
Set 4: Sound level meter, Vibrometer - Sound Meter Pro
Set 5: Flashlight, Magnifier, Mirror - Smart Light Pro
See the video below for live demo
*Note: Your Smartphone/Tablet must have magnetic sensor for some tools to work such as metal detector
Unfortunately, This is not a free app...but there is a round about method to grab those tools. Instead of downloading smart tools app which is an all-in-one tool app, we can download the each tool developed by the same developer for free. The Developer is only charging for this All-in-One App. You can find these individual tool apps in the "More from Developer" category.