A Mac, apple magic trackpad, the free bettertouchtool software for that trackpad and Amazing Slow Downer. Try it. Fastest way I've found to learn, practice, rehearse on guitar without stopping to use a mouse/keyboard, and without the speed limits of Riff Station, or lack of features, user-friendliness, or bloated features of other products.
!Slow down music with Mac and Windows computers!
BetterTouchTool
ALL the software controls have keyboard shortcuts, so everything you need while playing can be mapped to the trackpad, fast/slow, volume, pause, stop, rewind, play, loop nudging, speed presets, toggle EQ, toggle stereo, center/left/right hard pan, slowdown processing type, toggle loop on/off etc. Highly recommended for mac users or PC guys who have a programmable trackpad.
*edit* You can also use your phone as the trackpad. BetterTouchTool has an upgrade so you can control the SlowDowner software from iPhone over bluetooth.