Here is a great app for an iPad or iPhone if you want to do double system sound with your GH1 or GH2.
Little expensive but could be useful.

Movie?Slate (Clapperboard & Shot Log) for iPhone, iPod touch, and iPad on the iTunes App Store (http://itunes.apple.com/us/app/id320315888?mt=8)

almost the same and free
DSLR Slate for iPhone, iPod touch, and iPad on the iTunes App Store (http://itunes.apple.com/us/app/dslr-slate/id374241045?mt=8)

There's one of these for Droid but it doesn't give a sound cue or animate the slate snapping shut so what use is it? Is the iPhone version fully functional?

I would think so, the iPad one is.

There's one of these for Droid but it doesn't give a sound cue or animate the slate snapping shut so what use is it? Is the iPhone version fully functional?

Hi Brian -- I use SL Digislate for Android -- a great little app that gives a sound cue, provides a clock time hack to a hundredth of a second and animates the slate snapping shut.

SL Digislate - Stephen's Android Apps and Other Projects (http://sites.google.com/site/srlappsproject/home/sl-digislate)

It's available either on the website or on Android Market for $9.99

Hi Brian -- I use SL Digislate for Android -- a great little app that gives a sound cue, provides a clock time hack to a hundredth of a second and animates the slate snapping shut.

SL Digislate - Stephen's Android Apps and Other Projects (http://sites.google.com/site/srlappsproject/home/sl-digislate)

It's available either on the website or on Android Market for $9.99

I tried it and returned it. It's a nice enough application, but the evaluation period is only 15 minutes so there's no time to test it, my main concern is that the audio BEEP isn't strong enough for the mic to pick up. But since I only had 15 min, I'll never know.