Android (rooted): On-screen navigation controls are a great alternative to physical buttons. Xtended Navbar provides easy access to not only home, back and settings buttons, but also music controls and toggles.
Swipe from either edge of the navbar at the bottom of the screen to access other buttons. Edit the module's settings to switch which buttons appear when you swipe left or right. Just fire up the app using its shortcut, select the settings you want to use, then restart your handset.
Xtended NavBar is available free of charge, but if you make a small donation, you can also access frequently used apps. At the moment, the module only works in portrait mode but the developer is working on adding landscape support. Xtended Navbar may not work with all devices that already have third-party navbars, or customised ROMs according to some users in the XDA Developers Forum. Stock Android 4.2.2, 4.3 and 4.4.2 proved problem-free for me.