It's a combined mobile/web location-based content and social network. The basic idea is something like:
i) Take a photo using the app (or add an existing photo to the app) on your phone - this is called "PlaceMe"
ii) Upload to GyPSii website with location attached (using GPS)
iii) Check out what's around your current position ("Search") or where your GyPSii friends are ("SpaceMe"), see them on a map, share Places with them, etc etc
You can sign up using the mobile app or on the web at GyPSii Webtop: Me. When you get home or back to the office, you can log in to GyPSii again, check out everyone else's places, and edit any Places you've created.
We've only just got the S60 version back from certification (the Windows Mobile version's been available a few weeks) and are very excited to hear what people think! Please let us know, either in this thread or by clicking the support link at the bottom of our website.
We'd also be curious to hear from anyone who's got a N82 device - we haven't tested on this phone yet!