Panasonic ZR1 battery.
If you've bought one of Panasonic's new cameras that have firmware to prevent using generic batteries the D'OH! is over.
I saw this on ebay the other week and bought it as it claimed to be compatible with the recent firmware. They're right, it works on my new ZR1 which only has the new firmware.
The downside is that it's about double the price of the cheap generics that won't work but is about a third the price of genuine.