Browsing through the P2 forum I’ve discovered a mention of a fantastic child theme for P2 by Jonathan Warren.

Child themes are notoriously tricky to get to work with the P2 parent theme, so you’ll have to do a bit of fiddling with some core files – but the results are great.

Check out a demo of P2 Responsive here, or download the Child Theme from GItHub (comes with instructions on how to make it work).

You may also be interested in Jonathan’s release post about his work.