Zune TunePower from Belkin
The Belkin TunePower is a rechargeable power supply for the Zune. A flat power cable with a Zune USB plug hangs from the battery compartment. The device comes with a separate AC power supply for charging the Tunpower itself.
The Zune will snap right into the Tunepower, and the case does offer some level of protection, especially for the rear and corners of the Zune.
A handy kickstand flips out the back, although it may appear aluminum, it's actually plastic. Also on the rear is a power indicator LED light which displays green when the Tunepower is fully charged.
The form factor is nice because everything is integrated. The Tunepower is rated to add 6-12 hours of battery life to the Zune. This range seemed accurate with our unscientific testing.
In conclusion the Tunepower is recommended for travelers, not for daily use. The device essentially doubles the size of the Zune and should not be compared to a Zune case.
Currently the MSRP is $59.99 but internet shoppers can often find it for less.