I was kind of surprised by the number of additional products people in the group suggested as delivery tools for trax.
Here are two more:

1) GEM pole speakers have a USB port that will take a thumb drive full of MP3s (or WAVS I suppose). You also get a hand-held play device. Since anybody playing live is probably going to need a PA anyway, this is one way to make trax delivery a built-in part of your system

LINK TO GEM SPEAKERS



2) another device capable of delivering backing tracks is Roland's GR-55 guitar synth. It has a USB port and built in pedal control for navigating and playing songs stored on the USB drive

LINK TO GR-55


if you know of more such devices, please add them to the list!