Rekordbox DJ app from Pioneer now allows for Dropbox cloud syncing

Rekordbox is an app compatible with all Pioneer DJ hardware and available for Windows and macOS, with an accompanying mobile app that allows for tweaking of memory cues and loops, among other features, available to Android and iOS users.
Now Pioneer has partnered with cloud service Dropbox to let users sync their library and access it from multiple devices, with subscription plans available at prices of up to $14.99 per month. There is a discount to those subscription plans at the moment however, lowering the Creative plan to $9.99 until July 13th. In addition, a 30-day free trial is also available to new users, with an option to cancel anytime.
There are also more enthusiast-oriented and fully-functional mobile DJ apps out there, such as edjing, available at $9 for both Android and iOS users, and DJ Studio 5, which is only on Android and features a free demo.
For full-blown music production on your phone or tablet, I would recommend FL Studio Mobile on Android, priced at $15, and the free iPad and iPhone exclusive GarageBand. Both apps approach music making differently, but are fairly easy to pick up and use, especially the latter.