It's an add on for a guitar game with a 3/4 plastic guitar with real strings (Power Gig: Rise of the Six String).
I wasn't sure what to make of it, but it was five dollars. I couldn't leave without at least looking in the box. So I asked the guy behind the counter and while he couldn't let me take it out of the wrapping, he opened the box and lo and behold, there was a 1/4 to 1/4 cable in there!
So now I have a pocket amp! It has one button: power. the volume is controlled by your guitar's volume, which at max is all crunchy, and dialed down a bit is pretty clean (when played with a Telecaster). Five dollar pocket amp! I wonder how it compares to the Marshall one?