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.