Here are some of those tools
Spirit Level or type Spirit Level in Google, it uses the smart phones gravity sensors to guide the bubble. Very clever.
Tuner It will tell you what note your voice or musical key is making. It listens to the microphone and detects the pitch of the sound. Wow. You can tune a piano or train your voice to hit different frequencies.
Dice Roller, you can roll a dice and add different types of dice. If you lost your dice, don't worry. You can even play liars dice.
Coin Flipper, You can flip a coin if you didn't have one.
We live in an amazing world where access to useful things can be low cost or free. I learnt many things from the internet. Very useful.
