One thing I've considered are a Bluetooth A2DP sender and receiver, many of which can work with a "normal" pair of headphones. These are available from a bunch of no-name companies for $20-$30.

What I currently do, which makes me quite happy, is that I have a really long cable (http://www.amazon.com/Grado-Extension-Cable-4-57m-Headphone/dp/B0006DPNNK). No batteries. No worries.