MP3AMP
It uses a standard 3.5mm (1/8") audio jack that makes it compatible with sound-producing equipment.

MP3AMP  uses a standard 3.5mm (1/8") audio jack that makes it compatible with sound-producing equipment.

In our Ham Radio Lab, we use it for an audio signal-tracer, but other members of our staff use them with their MP3 players and iPods.  Shielded cable with 3.5mm stereo plug attached is 36 inches.

It uses a standard 3.5mm (1/8") audio jack that makes it compatible with virtually all sound-producing electronics and it comes in an airtight shell for these dusty days.  It's powered by one 9 volt battery.