iOS:
https://apps.apple.com/us/app/instuner-free-chromatic-tuner/id603425027
Android:
https://play.google.com/store/apps/details?id=com.finestandroid.tunner&hl=en_US
Computer:
https://tuner.ninja/
https://apps.apple.com/us/app/pro-metronome-tempo-beat-subdivision-polyrhythm/id477960671
https://play.google.com/store/apps/details?id=com.eumlab.android.prometronome&hl=en_US
https://www.google.com/search?q=metronome