Yes, it's possible! You'll need to update your SMC Firmware using the following packages. (Edit: links removed. These packages are no longer needed as Power Nap support has been officially added in the Mac OS X 10.8.2 update) After installation, the Power Nap settings will appear in the Energy Saver preferences pane. Disclaimer: Install at your own risk! These updates were pushed out during the Mountain Lion beta, but for whatever reason Apple has not yet made them generally available via software update. It's possible that issues were discovered with the updates during the ML beta, or maybe they just decided at the last minute not to release the update for older Macs. Warning: These files are for the MacBook Air (Late 2010) only. Do not attempt to install them on other models!