SCDJ

Sometimes some of us, djs, just have an urge to mix a couple of tracks.
And when all you have is your phone, just... use SCDJ.
You can spin tracks or playlists straight from SoundCloud.
All the buttons and faders are familiar, you'll figure it out!

And don't trust the bpm analyser. I still can't make it better. Trust your ears.
Some tracks cannot load from SoundCloud this way, but most will.