This app was mentioned in 2 comments, with an average of 8.50 upvotes
To add to the other comment, I like to use an android app called Chordbot to play back chord progressions. It's a bit of a backing track generator.
You can find it here. There's also a free version available called Chordbot Lite, which lacks some features of the full version, but it doesn't feature any ads and is sufficient for a lot of situations.
Andropid user here. Here's what I use.
Caustic It's basically a full featured sequencer with multiple styles of synths and a drum machine. Oh, and a vocoder. It's amazing for the price.
Chordbot Chord progression sketch tool. Get in on the beta as the dev has finally started to support setting the Key of a chord progression.
Nanoloop It's basically a step sequencer based off of old Gameboy chiptune sequencers.
And lastly I use Dropbox and Dropbox sync to keep my song ideas synced to my phone for listening back and I keep notes in Trello.