This will listen to the frequencies from your phones' microphone and display them on the screen, allowing easy tuning of drums. It shows arrow buttons on whether to tune up or down.
It cuts down the frequencies detected to eliminate overtones, which can confuse tuning.
This App is entirely free with no ads.

This will show the loudest frequency detected and an icon indicating whether to tune up or down. A green tick indicates it is correctly tuned, green up or down arrow indicates the drum is close, red arrows indicate it is further out.
There is also a full range frequency detector.

It allows you to hide the default drums and add customised ones.
It can be used for tuning most other instruments, too.