This app was mentioned in 4 comments, with an average of 1.50 upvotes
This Metronome app for Android has acceleration: https://play.google.com/store/apps/details?id=com.keuwl.metronome
Free apps! Stuff I use every day.
Best metronome I've seen for Android devices ==> https://play.google.com/store/apps/details?id=com.keuwl.metronome
Best (not simplest) tuner ==> https://play.google.com/store/apps/details?id=org.galexander.tunertime&hl=en_US
VLC is great for playing along with video or audio media. It has controls to queue and loop content as well as vary the tempo and pitch. Also good for saving playlists of stuff you're working on.
Try this one.