djay 2, like its predecessor, is one of the best iOS DJ apps of all time.  Better yet, it has recently been ported to Android and is now available on both platforms!  Its excellent interface allows you to successfully utilize it to carry out DJ-related tasks like track syncing and mixing. Further features include: 

• Import abilities from your music library OR Spotify 
• Match - This feature can automatically find music that goes well with your current track.  Typically by genre and beats per minute (bpm).
• Effects
• Cue Points