There is another tool that almost nobody uses. It's not cheap but it stores backing tracks and is easily triggered.

The Roland SPD-SX has 2 GB of storage. If you need more, you can use a thumb drive.

You simply create your music, convert the files to WAV format, load them and trigger playback with a foot switch, drum pad or built in pad.

The nice thing about it is that it's one piece of gear.