i receive the same email today too ^^ :

Thanks for your email and enquiry for a Mugen Power Battery for the Nokia N900. At this moment, we are developing a high-performance battery for this model. As soon as we have any further information about final specification and a release date, we will inform you by email. Thanks for visiting our website and interest in our products.

If you have any questions or need more information, please do not hesitate to contact us. We will be happy to assist.

Merry Christmas and we wish you a lot of power in the New Year!

Kindest regards,
Bert
Support Department
Mugen Power Batteries Europe