I was browsing through a list of products that were using EnOcean, and found some neat examples I thought were worth sharing. They are all commercial products that use self-powered sensors in novel ways.
Since these products all use Enocean technology inside, they should be compatible with the EnOcean Pi or the EnOcean USB gateways (assuming the frequencies are the same).
Wireless window magnetic contact sensors are plentiful, but the SecuSignal window handle takes it a step further. The position of the handle is transmitted, so you can tell if the window is open or locked.
Another such sensor comes from SODA GmbH. Their wireless handle also measures temperature, humidity and ambient light.
The IQseat reports its changes in state from unoccupied to occupied and vice versa. It's promoted as useful for security and HVAC applications. I imagine it could also be handy for occupational health - to let employees know when they have been sitting down for too long - or perhaps just to detect when someone is sitting in your favourite chair!
Also available from the same company is the IQmat mattress sensor.
The CT Clamp from Pressac lets you wireless measure the current usage. The sensor powers itself from the cable it's measuring.